draft-ietf-hybi-thewebsocketprotocol-06.txt   draft-ietf-hybi-thewebsocketprotocol-07.txt 
HyBi Working Group I. Fette HyBi Working Group I. Fette
Internet-Draft Google, Inc. Internet-Draft Google, Inc.
Intended status: Standards Track February 25, 2011 Intended status: Standards Track April 22, 2011
Expires: August 29, 2011 Expires: October 24, 2011
The WebSocket protocol The WebSocket protocol
draft-ietf-hybi-thewebsocketprotocol-06 draft-ietf-hybi-thewebsocketprotocol-07
Abstract Abstract
The WebSocket protocol enables two-way communication between a user The WebSocket protocol enables two-way communication between a user
agent running untrusted code running in a controlled environment to a agent running untrusted code running in a controlled environment to a
remote host that has opted-in to communications from that code. The remote host that has opted-in to communications from that code. The
security model used for this is the Origin-based security model security model used for this is the Origin-based security model
commonly used by Web browsers. The protocol consists of an initial commonly used by Web browsers. The protocol consists of an initial
handshake followed by basic message framing, layered over TCP. The handshake followed by basic message framing, layered over TCP. The
goal of this technology is to provide a mechanism for browser-based goal of this technology is to provide a mechanism for browser-based
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 29, 2011. This Internet-Draft will expire on October 24, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Background . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Background . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Protocol overview . . . . . . . . . . . . . . . . . . . . 4 1.2. Protocol overview . . . . . . . . . . . . . . . . . . . . 4
1.3. Opening handshake . . . . . . . . . . . . . . . . . . . . 6 1.3. Opening handshake . . . . . . . . . . . . . . . . . . . . 6
1.4. Closing handshake . . . . . . . . . . . . . . . . . . . . 8 1.4. Closing handshake . . . . . . . . . . . . . . . . . . . . 8
1.5. Design philosophy . . . . . . . . . . . . . . . . . . . . 9 1.5. Design philosophy . . . . . . . . . . . . . . . . . . . . 9
1.6. Security model . . . . . . . . . . . . . . . . . . . . . . 9 1.6. Security model . . . . . . . . . . . . . . . . . . . . . . 10
1.7. Relationship to TCP and HTTP . . . . . . . . . . . . . . . 10 1.7. Relationship to TCP and HTTP . . . . . . . . . . . . . . . 10
1.8. Establishing a connection . . . . . . . . . . . . . . . . 10 1.8. Establishing a connection . . . . . . . . . . . . . . . . 11
1.9. Subprotocols using the WebSocket protocol . . . . . . . . 11 1.9. Subprotocols using the WebSocket protocol . . . . . . . . 11
2. Conformance requirements . . . . . . . . . . . . . . . . . . . 12 2. Conformance requirements . . . . . . . . . . . . . . . . . . . 13
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 12 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 13
3. WebSocket URIs . . . . . . . . . . . . . . . . . . . . . . . . 14 3. WebSocket URIs . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1. Parsing WebSocket URIs . . . . . . . . . . . . . . . . . . 14 3.1. Parsing WebSocket URIs . . . . . . . . . . . . . . . . . . 15
3.2. Constructing WebSocket URIs . . . . . . . . . . . . . . . 15 3.2. Constructing WebSocket URIs . . . . . . . . . . . . . . . 16
3.3. Valid WebSocket URIs . . . . . . . . . . . . . . . . . . . 15 3.3. Valid WebSocket URIs . . . . . . . . . . . . . . . . . . . 16
4. Data Framing . . . . . . . . . . . . . . . . . . . . . . . . . 16 4. Data Framing . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.2. Client-to-Server Masking . . . . . . . . . . . . . . . . . 16 4.2. Base Framing Protocol . . . . . . . . . . . . . . . . . . 17
4.3. Base Framing Protocol . . . . . . . . . . . . . . . . . . 17 4.3. Client-to-Server Masking . . . . . . . . . . . . . . . . . 20
4.4. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 19 4.4. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 21
4.5. Control Frames . . . . . . . . . . . . . . . . . . . . . . 21 4.5. Control Frames . . . . . . . . . . . . . . . . . . . . . . 23
4.5.1. Close . . . . . . . . . . . . . . . . . . . . . . . . 21 4.5.1. Close . . . . . . . . . . . . . . . . . . . . . . . . 23
4.5.2. Ping . . . . . . . . . . . . . . . . . . . . . . . . . 21 4.5.2. Ping . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.5.3. Pong . . . . . . . . . . . . . . . . . . . . . . . . . 22 4.5.3. Pong . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.6. Data Frames . . . . . . . . . . . . . . . . . . . . . . . 22 4.6. Data Frames . . . . . . . . . . . . . . . . . . . . . . . 24
4.7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 22 4.7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.8. Extensibility . . . . . . . . . . . . . . . . . . . . . . 23 4.8. Extensibility . . . . . . . . . . . . . . . . . . . . . . 25
5. Opening Handshake . . . . . . . . . . . . . . . . . . . . . . 24 5. Opening Handshake . . . . . . . . . . . . . . . . . . . . . . 27
5.1. Client Requirements . . . . . . . . . . . . . . . . . . . 24 5.1. Client Requirements . . . . . . . . . . . . . . . . . . . 27
5.2. Server-side requirements . . . . . . . . . . . . . . . . . 28 5.2. Server-side requirements . . . . . . . . . . . . . . . . . 31
5.2.1. Reading the client's opening handshake . . . . . . . . 29 5.2.1. Reading the client's opening handshake . . . . . . . . 32
5.2.2. Sending the server's opening handshake . . . . . . . . 29 5.2.2. Sending the server's opening handshake . . . . . . . . 32
6. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 32 6. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 36
6.1. Handling errors in UTF-8 from the server . . . . . . . . . 32 6.1. Handling errors in UTF-8 from the server . . . . . . . . . 36
6.2. Handling errors in UTF-8 from the client . . . . . . . . . 32 6.2. Handling errors in UTF-8 from the client . . . . . . . . . 36
7. Closing the connection . . . . . . . . . . . . . . . . . . . . 33 7. Closing the connection . . . . . . . . . . . . . . . . . . . . 37
7.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 33 7.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 37
7.1.1. Close the WebSocket Connection . . . . . . . . . . . . 33 7.1.1. Close the WebSocket Connection . . . . . . . . . . . . 37
7.1.2. Start the WebSocket Closing Handshake . . . . . . . . 33 7.1.2. Start the WebSocket Closing Handshake . . . . . . . . 37
7.1.3. The WebSocket Connection Is Closed . . . . . . . . . . 33 7.1.3. The WebSocket Connection Is Closed . . . . . . . . . . 37
7.1.4. Fail the WebSocket Connection . . . . . . . . . . . . 33 7.1.4. Fail the WebSocket Connection . . . . . . . . . . . . 37
7.2. Abnormal closures . . . . . . . . . . . . . . . . . . . . 34 7.2. Abnormal closures . . . . . . . . . . . . . . . . . . . . 37
7.2.1. Client-initiated closure . . . . . . . . . . . . . . . 34 7.2.1. Client-initiated closure . . . . . . . . . . . . . . . 38
7.2.2. Server-initiated closure . . . . . . . . . . . . . . . 34 7.2.2. Server-initiated closure . . . . . . . . . . . . . . . 38
7.3. Normal closure of connections . . . . . . . . . . . . . . 34 7.3. Normal closure of connections . . . . . . . . . . . . . . 38
7.4. Status codes . . . . . . . . . . . . . . . . . . . . . . . 34 7.4. Status codes . . . . . . . . . . . . . . . . . . . . . . . 38
7.4.1. Defined Status Codes . . . . . . . . . . . . . . . . . 34 7.4.1. Defined Status Codes . . . . . . . . . . . . . . . . . 38
7.4.2. Reserved status code ranges . . . . . . . . . . . . . 35 7.4.2. Reserved status code ranges . . . . . . . . . . . . . 39
8. Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . 37 8. Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . 41
8.1. Negotiating extensions . . . . . . . . . . . . . . . . . . 37 8.1. Negotiating extensions . . . . . . . . . . . . . . . . . . 41
8.2. Known extensions . . . . . . . . . . . . . . . . . . . . . 38 8.2. Known extensions . . . . . . . . . . . . . . . . . . . . . 42
8.2.1. Compression . . . . . . . . . . . . . . . . . . . . . 38 8.2.1. Compression . . . . . . . . . . . . . . . . . . . . . 42
9. Security considerations . . . . . . . . . . . . . . . . . . . 40 9. Security considerations . . . . . . . . . . . . . . . . . . . 44
10. IANA considerations . . . . . . . . . . . . . . . . . . . . . 42 10. IANA considerations . . . . . . . . . . . . . . . . . . . . . 46
10.1. Registration of ws: scheme . . . . . . . . . . . . . . . . 42 10.1. Registration of ws: scheme . . . . . . . . . . . . . . . . 46
10.2. Registration of wss: scheme . . . . . . . . . . . . . . . 43 10.2. Registration of wss: scheme . . . . . . . . . . . . . . . 47
10.3. Registration of the "WebSocket" HTTP Upgrade keyword . . . 44 10.3. Registration of the "WebSocket" HTTP Upgrade keyword . . . 48
10.4. Sec-WebSocket-Key . . . . . . . . . . . . . . . . . . . . 44 10.4. Sec-WebSocket-Key . . . . . . . . . . . . . . . . . . . . 48
10.5. Sec-WebSocket-Extensions . . . . . . . . . . . . . . . . . 45 10.5. Sec-WebSocket-Extensions . . . . . . . . . . . . . . . . . 49
10.6. Sec-WebSocket-Accept . . . . . . . . . . . . . . . . . . . 46 10.6. Sec-WebSocket-Accept . . . . . . . . . . . . . . . . . . . 50
10.7. Sec-WebSocket-Origin . . . . . . . . . . . . . . . . . . . 46 10.7. Sec-WebSocket-Origin . . . . . . . . . . . . . . . . . . . 50
10.8. Sec-WebSocket-Protocol . . . . . . . . . . . . . . . . . . 47 10.8. Sec-WebSocket-Protocol . . . . . . . . . . . . . . . . . . 51
10.9. Sec-WebSocket-Version . . . . . . . . . . . . . . . . . . 47 10.9. Sec-WebSocket-Version . . . . . . . . . . . . . . . . . . 51
11. Using the WebSocket protocol from other specifications . . . . 49 11. Using the WebSocket protocol from other specifications . . . . 53
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 50 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 54
13. Appendix: List of Changes . . . . . . . . . . . . . . . . . . 51 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 55
13.1. Changes from -05 to -06 . . . . . . . . . . . . . . . . . 51 13.1. Normative References . . . . . . . . . . . . . . . . . . . 55
14. Normative References . . . . . . . . . . . . . . . . . . . . . 53 13.2. Informative References . . . . . . . . . . . . . . . . . . 56
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 55 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 57
1. Introduction 1. Introduction
1.1. Background 1.1. Background
_This section is non-normative._ _This section is non-normative._
Historically, creating an instant messenger chat client as a Web Historically, creating an instant messenger chat client as a Web
application has required an abuse of HTTP to poll the server for application has required an abuse of HTTP to poll the server for
updates while sending upstream notifications as distinct HTTP calls. updates while sending upstream notifications as distinct HTTP
calls.[RFC6202]
This results in a variety of problems: This results in a variety of problems:
o The server is forced to use a number of different underlying TCP o The server is forced to use a number of different underlying TCP
connections for each client: one for sending information to the connections for each client: one for sending information to the
client, and a new one for each incoming message. client, and a new one for each incoming message.
o The wire protocol has a high overhead, with each client-to-server o The wire protocol has a high overhead, with each client-to-server
message having an HTTP header. message having an HTTP header.
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The handshake from the client looks as follows: The handshake from the client looks as follows:
GET /chat HTTP/1.1 GET /chat HTTP/1.1
Host: server.example.com Host: server.example.com
Upgrade: websocket Upgrade: websocket
Connection: Upgrade Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ== Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Origin: http://example.com Sec-WebSocket-Origin: http://example.com
Sec-WebSocket-Protocol: chat, superchat Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 6 Sec-WebSocket-Version: 7
The handshake from the server looks as follows: The handshake from the server looks as follows:
HTTP/1.1 101 Switching Protocols HTTP/1.1 101 Switching Protocols
Upgrade: websocket Upgrade: websocket
Connection: Upgrade Connection: Upgrade
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo= Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
Sec-WebSocket-Protocol: chat Sec-WebSocket-Protocol: chat
The leading line from the client follows the Request-Line format. The leading line from the client follows the Request-Line format.
The leading line from the server follows the Status-Line format. The The leading line from the server follows the Status-Line format. The
Request-Line and Status-Line productions are defined in [RFC2616]. Request-Line and Status-Line productions are defined in [RFC2616].
After the leading line in both cases come an unordered set of After the leading line in both cases come an unordered set of header
headers. The meaning of these headers is specified in Section 5 of fields. The meaning of these header fields is specified in Section 5
this document. Additional headers may also be present, such as of this document. Additional header fields may also be present, such
cookies required to identify the user. The format and parsing of as cookies [I-D.ietf-httpstate-cookie] required to identify the user.
headers is as defined in [RFC2616]. The format and parsing of headers is as defined in [RFC2616].
Once the client and server have both sent their handshakes, and if Once the client and server have both sent their handshakes, and if
the handshake was successful, then the data transfer part starts. the handshake was successful, then the data transfer part starts.
This is a two-way communication channel where each side can, This is a two-way communication channel where each side can,
independently from the other, send data at will. independently from the other, send data at will.
Clients and servers, after a successful handshake, transfer data back Clients and servers, after a successful handshake, transfer data back
and forth in conceptual units referred to in this specification as and forth in conceptual units referred to in this specification as
"messages". A message is a complete unit of data at an application "messages". A message is a complete unit of data at an application
level, with the expectation that many or most applications level, with the expectation that many or most applications
implementing this protocol (such as web user agents) provide APIs in implementing this protocol (such as web user agents) provide APIs in
terms of sending and receiving messages. The websocket message does terms of sending and receiving messages. The websocket message does
not necessarily correspond to a particular network layer framing, as not necessarily correspond to a particular network layer framing, as
a fragmented message may be coalesced, or vice versa, e.g. by an a fragmented message may be coalesced, or vice versa, e.g. by an
intermediary. intermediary.
Data is sent on the wire in the form of frames that have an Data is sent on the wire in the form of frames that have an
associated type. Broadly speaking, there are types for textual data, associated type. A message is composed of one or more frames, all of
which is interpreted as UTF-8 text, binary data (whose interpretation which contain the same type of data. Broadly speaking, there are
is left up to the application), and control frames, which are not types for textual data, which is interpreted as UTF-8 [RFC3629] text,
intended to carry data for the application, but instead for protocol- binary data (whose interpretation is left up to the application), and
level signaling, such as to signal that the connection should be control frames, which are not intended to carry data for the
closed. This version of the protocol defines six frame types and application, but instead for protocol-level signaling, such as to
leaves ten reserved for future use. signal that the connection should be closed. This version of the
protocol defines six frame types and leaves ten reserved for future
use.
The WebSocket protocol uses this framing so that specifications that The WebSocket protocol uses this framing so that specifications that
use the WebSocket protocol can expose such connections using an use the WebSocket protocol can expose such connections using an
event-based mechanism instead of requiring users of those event-based mechanism instead of requiring users of those
specifications to implement buffering and piecing together of specifications to implement buffering and piecing together of
messages manually. messages manually.
1.3. Opening handshake 1.3. Opening handshake
_This section is non-normative._ _This section is non-normative._
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clients talking to that server. To this end, the WebSocket client's clients talking to that server. To this end, the WebSocket client's
handshake is an HTTP Upgrade request: handshake is an HTTP Upgrade request:
GET /chat HTTP/1.1 GET /chat HTTP/1.1
Host: server.example.com Host: server.example.com
Upgrade: websocket Upgrade: websocket
Connection: Upgrade Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ== Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Origin: http://example.com Sec-WebSocket-Origin: http://example.com
Sec-WebSocket-Protocol: chat, superchat Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 6 Sec-WebSocket-Version: 7
Headers in the handshake are sent by the client in a random order; Headers in the handshake are sent by the client in a random order;
the order is not meaningful. the order is not meaningful.
The "Request-URI" of the GET method [RFC2616] is used to identify the
endpoint of the WebSocket connection, both to allow multiple domains
to be served from one IP address and to allow multiple WebSocket
endpoints to be served by a single server.
The client includes the hostname in the Host header of its handshake
as per [RFC2616], so that both the client and the server can verify
that they agree on which host is in use.
Additional headers are used to select options in the WebSocket Additional headers are used to select options in the WebSocket
protocol. Options available in this version are the subprotocol protocol. Options available in this version are the subprotocol
selector, |Sec-WebSocket-Protocol|, and |Cookie|, which can used for selector, |Sec-WebSocket-Protocol|, and |Cookie|, which can used for
sending cookies to the server (e.g. as an authentication mechanism). sending cookies to the server (e.g. as an authentication mechanism).
The |Sec-WebSocket-Protocol| request-header field can be used to The |Sec-WebSocket-Protocol| request-header field can be used to
indicate what subprotocols (application-level protocols layered over indicate what subprotocols (application-level protocols layered over
the WebSocket protocol) are acceptable to the client. The server the WebSocket protocol) are acceptable to the client. The server
selects one of the acceptable protocols and echoes that value in its selects one of the acceptable protocols and echoes that value in its
handshake to indicate that it has selected that protocol. handshake to indicate that it has selected that protocol.
Sec-WebSocket-Protocol: chat Sec-WebSocket-Protocol: chat
The "Request-URI" of the GET method [RFC2616] is used to identify the
endpoint of the WebSocket connection, both to allow multiple domains
to be served from one IP address and to allow multiple WebSocket
endpoints to be served by a single server.
The client includes the hostname in the Host header of its handshake
as per [RFC2616], so that both the client and the server can verify
that they agree on which host is in use.
The |Sec-WebSocket-Origin| header is used to protect against The |Sec-WebSocket-Origin| header is used to protect against
unauthorized cross-origin use of a WebSocket server by scripts using unauthorized cross-origin use of a WebSocket server by scripts using
the |WebSocket| API in a Web browser. The server is informed of the the |WebSocket| API in a Web browser. The server is informed of the
script origin generating the WebSocket connection request. If the script origin generating the WebSocket connection request. If the
server does not wish to accept connections from this origin, it can server does not wish to accept connections from this origin, it can
choose to abort the connection. This header is sent by browser choose to abort the connection. This header is sent by browser
clients, for non-browser clients this header may be sent if it makes clients, for non-browser clients this header may be sent if it makes
sense in the context of those clients. sense in the context of those clients.
Finally, the server has to prove to the client that it received the Finally, the server has to prove to the client that it received the
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crafted packets using |XMLHttpRequest| or a |form| submission. crafted packets using |XMLHttpRequest| or a |form| submission.
To prove that the handshake was received, the server has to take two To prove that the handshake was received, the server has to take two
pieces of information and combine them to form a response. The first pieces of information and combine them to form a response. The first
piece of information comes from the |Sec-WebSocket-Key| header in the piece of information comes from the |Sec-WebSocket-Key| header in the
client handshake: client handshake:
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ== Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
For this header, the server has to take the value (as present in the For this header, the server has to take the value (as present in the
header, e.g. the base64-encoded version), and concatenate this with header, e.g. the base64-encoded [RFC4648] version minus leading and
the GUID "258EAFA5-E914-47DA-95CA-C5AB0DC85B11" in string form, which trailing whitespace), and concatenate this with the GUID "258EAFA5-
is unlikely to be used by network endpoints that do not understand E914-47DA-95CA-C5AB0DC85B11" in string form, which is unlikely to be
the WebSocket protocol. A SHA-1 hash, base64-encoded, of this used by network endpoints that do not understand the WebSocket
concatenation is then returned in the server's handshake protocol. A SHA-1 hash, base64-encoded, of this concatenation is
[FIPS.180-2.2002]. then returned in the server's handshake [FIPS.180-2.2002].
Concretely, if as in the example above, header |Sec-WebSocket-Key| Concretely, if as in the example above, header |Sec-WebSocket-Key|
had the value "dGhlIHNhbXBsZSBub25jZQ==", the server would had the value "dGhlIHNhbXBsZSBub25jZQ==", the server would
concatenate the string "258EAFA5-E914-47DA-95CA-C5AB0DC85B11" to form concatenate the string "258EAFA5-E914-47DA-95CA-C5AB0DC85B11" to form
the string "dGhlIHNhbXBsZSBub25jZQ==258EAFA5-E914-47DA-95CA- the string "dGhlIHNhbXBsZSBub25jZQ==258EAFA5-E914-47DA-95CA-
C5AB0DC85B11". The server would then take the SHA-1 hash of this, C5AB0DC85B11". The server would then take the SHA-1 hash of this,
giving the value 0xb3 0x7a 0x4f 0x2c 0xc0 0x62 0x4f 0x16 0x90 0xf6 giving the value 0xb3 0x7a 0x4f 0x2c 0xc0 0x62 0x4f 0x16 0x90 0xf6
0x46 0x06 0xcf 0x38 0x59 0x45 0xb2 0xbe 0xc4 0xea. This value is 0x46 0x06 0xcf 0x38 0x59 0x45 0xb2 0xbe 0xc4 0xea. This value is
then base64-encoded, to give the value "s3pPLMBiTxaQ9kYGzzhZRbK+ then base64-encoded, to give the value "s3pPLMBiTxaQ9kYGzzhZRbK+
xOo=". This value would then be echoed in the header |Sec-WebSocket- xOo=". This value would then be echoed in the header |Sec-WebSocket-
Accept|. Accept|.
The handshake from the server is much simpler than the client The handshake from the server is much simpler than the client
handshake. The first line is an HTTP Status-Line, with the status handshake. The first line is an HTTP Status-Line, with the status
code 101: code 101:
HTTP/1.1 101 Switching Protocols HTTP/1.1 101 Switching Protocols
Any status code other than 101 MUST be treated as a failure if Any status code other than 101 indicates that the WebSocket handshake
semantics of that status code are not defined in the context of a has not completed, and that the semantics of HTTP still apply. The
WebSocket connection, and the websocket connection aborted. The
headers follow the status code. headers follow the status code.
The |Connection| and |Upgrade| headers complete the HTTP Upgrade. The |Connection| and |Upgrade| headers complete the HTTP Upgrade.
The |Sec-WebSocket-Accept| header indicates whether the server is The |Sec-WebSocket-Accept| header indicates whether the server is
willing to accept the connection. If present, this header must willing to accept the connection. If present, this header must
include a hash of the client's nonce sent in |Sec-WebSocket-Key| include a hash of the client's nonce sent in |Sec-WebSocket-Key|
along with a predefined GUID. Any other value must not be along with a predefined GUID. Any other value must not be
interpreted as an acceptance of the connection by the server. interpreted as an acceptance of the connection by the server.
HTTP/1.1 101 Switching Protocols HTTP/1.1 101 Switching Protocols
skipping to change at page 8, line 29 skipping to change at page 8, line 37
These fields are checked by the Web browser when it is acting as a These fields are checked by the Web browser when it is acting as a
|WebSocket| client for scripted pages. If the |Sec-WebSocket-Accept| |WebSocket| client for scripted pages. If the |Sec-WebSocket-Accept|
value does not match the expected value, or if the header is missing, value does not match the expected value, or if the header is missing,
or if the HTTP status code is not 101, the connection will not be or if the HTTP status code is not 101, the connection will not be
established and WebSockets frames will not be sent. established and WebSockets frames will not be sent.
Option fields can also be included. In this version of the protocol, Option fields can also be included. In this version of the protocol,
the main option field is |Sec-WebSocket-Protocol|, which indicates the main option field is |Sec-WebSocket-Protocol|, which indicates
the subprotocol that the server has selected. Web browsers verify the subprotocol that the server has selected. Web browsers verify
that the server included one of the values as was specified in the that the server included one of the values as was specified in the
|WebSocket| constructor. A server that speaks multiple subprotocols WebSocket client' handshake. A server that speaks multiple
has to make sure it selects one based on the client's handshake and subprotocols has to make sure it selects one based on the client's
specifies it in its handshake. handshake and specifies it in its handshake.
Sec-WebSocket-Protocol: chat Sec-WebSocket-Protocol: chat
The server can also set cookie-related option fields to _set_ The server can also set cookie-related option fields to _set_
cookies, as in HTTP. cookies, as in HTTP.
1.4. Closing handshake 1.4. Closing handshake
_This section is non-normative._ _This section is non-normative._
skipping to change at page 9, line 18 skipping to change at page 9, line 26
discards any further data received. discards any further data received.
It is safe for both peers to initiate this handshake simultaneously. It is safe for both peers to initiate this handshake simultaneously.
The closing handshake is intended to replace the TCP closing The closing handshake is intended to replace the TCP closing
handshake (FIN/ACK), on the basis that the TCP closing handshake is handshake (FIN/ACK), on the basis that the TCP closing handshake is
not always reliable end-to-end, especially in the presence of man-in- not always reliable end-to-end, especially in the presence of man-in-
the-middle proxies and other intermediaries. the-middle proxies and other intermediaries.
By sending a close frame and waiting for a close frame in response, By sending a close frame and waiting for a close frame in response,
certain cases are avoided where data may be unnecessarily lost. For
instance, on some platforms, if a socket is closed with data in the
receive queue, a RST packet is sent, which will then cause recv() to
fail for the party that received the RST, even if there was data
waiting to be read.
1.5. Design philosophy 1.5. Design philosophy
_This section is non-normative._ _This section is non-normative._
The WebSocket protocol is designed on the principle that there should The WebSocket protocol is designed on the principle that there should
be minimal framing (the only framing that exists is to make the be minimal framing (the only framing that exists is to make the
protocol frame-based instead of stream-based, and to support a protocol frame-based instead of stream-based, and to support a
distinction between Unicode text and binary frames). It is expected distinction between Unicode text and binary frames). It is expected
that metadata would be layered on top of WebSocket by the application that metadata would be layered on top of WebSocket by the application
skipping to change at page 9, line 41 skipping to change at page 10, line 5
Conceptually, WebSocket is really just a layer on top of TCP that Conceptually, WebSocket is really just a layer on top of TCP that
adds a Web "origin"-based security model for browsers; adds an adds a Web "origin"-based security model for browsers; adds an
addressing and protocol naming mechanism to support multiple services addressing and protocol naming mechanism to support multiple services
on one port and multiple host names on one IP address; layers a on one port and multiple host names on one IP address; layers a
framing mechanism on top of TCP to get back to the IP packet framing mechanism on top of TCP to get back to the IP packet
mechanism that TCP is built on, but without length limits; and re- mechanism that TCP is built on, but without length limits; and re-
implements the closing handshake in-band. Other than that, it adds implements the closing handshake in-band. Other than that, it adds
nothing. Basically it is intended to be as close to just exposing nothing. Basically it is intended to be as close to just exposing
raw TCP to script as possible given the constraints of the Web. It's raw TCP to script as possible given the constraints of the Web. It's
also designed in such a way that its servers can share a port with also designed in such a way that its servers can share a port with
HTTP servers, by having its handshake be a valid HTTP Upgrade HTTP servers, by having its handshake be a valid HTTP Upgrade request
handshake also. mechanism also.
The protocol is intended to be extensible; future versions will The protocol is intended to be extensible; future versions will
likely introduce additional concepts such as multiplexing. likely introduce additional concepts such as multiplexing.
1.6. Security model 1.6. Security model
_This section is non-normative._ _This section is non-normative._
The WebSocket protocol uses the origin model used by Web browsers to The WebSocket protocol uses the origin model used by Web browsers to
restrict which Web pages can contact a WebSocket server when the restrict which Web pages can contact a WebSocket server when the
WebSocket protocol is used from a Web page. Naturally, when the WebSocket protocol is used from a Web page. Naturally, when the
WebSocket protocol is used by a dedicated client directly (i.e. not WebSocket protocol is used by a dedicated client directly (i.e. not
from a Web page through a Web browser), the origin model is not from a Web page through a Web browser), the origin model is not
useful, as the client can provide any arbitrary origin string. useful, as the client can provide any arbitrary origin string.
This protocol is intended to fail to establish a connection with This protocol is intended to fail to establish a connection with
servers of pre-existing protocols like SMTP or HTTP, while allowing servers of pre-existing protocols like SMTP [RFC5321] and HTTP, while
HTTP servers to opt-in to supporting this protocol if desired. This allowing HTTP servers to opt-in to supporting this protocol if
is achieved by having a strict and elaborate handshake, and by desired. This is achieved by having a strict and elaborate
limiting the data that can be inserted into the connection before the handshake, and by limiting the data that can be inserted into the
handshake is finished (thus limiting how much the server can be connection before the handshake is finished (thus limiting how much
influenced). the server can be influenced).
It is similarly intended to fail to establish a connection when data It is similarly intended to fail to establish a connection when data
from other protocols, especially HTTP, is sent to a WebSocket server, from other protocols, especially HTTP, is sent to a WebSocket server,
for example as might happen if an HTML |form| were submitted to a for example as might happen if an HTML |form| were submitted to a
WebSocket server. This is primarily achieved by requiring that the WebSocket server. This is primarily achieved by requiring that the
server prove that it read the handshake, which it can only do if the server prove that it read the handshake, which it can only do if the
handshake contains the appropriate parts which themselves can only be handshake contains the appropriate parts which themselves can only be
sent by a WebSocket handshake. In particular, at the time of writing sent by a WebSocket handshake. In particular, at the time of writing
of this specification, fields starting with |Sec-| cannot be set by of this specification, fields starting with |Sec-| cannot be set by
an attacker from a Web browser using only HTML and JavaScript APIs an attacker from a Web browser using only HTML and JavaScript APIs
such as |XMLHttpRequest|. such as |XMLHttpRequest|.
1.7. Relationship to TCP and HTTP 1.7. Relationship to TCP and HTTP
_This section is non-normative._ _This section is non-normative._
The WebSocket protocol is an independent TCP-based protocol. Its The WebSocket protocol is an independent TCP-based protocol. Its
only relationship to HTTP is that its handshake is interpreted by only relationship to HTTP is that its handshake is interpreted by
HTTP servers as an Upgrade request. HTTP servers as an Upgrade request.
Based on the expert recommendation of the IANA, the WebSocket By default the WebSocket protocol uses port 80 for regular WebSocket
protocol by default uses port 80 for regular WebSocket connections connections and port 443 for WebSocket connections tunneled over TLS
and port 443 for WebSocket connections tunneled over TLS. [RFC2818].
1.8. Establishing a connection 1.8. Establishing a connection
_This section is non-normative._ _This section is non-normative._
When a connection is to be made to a port that is shared by an HTTP When a connection is to be made to a port that is shared by an HTTP
server (a situation that is quite likely to occur with traffic to server (a situation that is quite likely to occur with traffic to
ports 80 and 443), the connection will appear to the HTTP server to ports 80 and 443), the connection will appear to the HTTP server to
be a regular GET request with an Upgrade offer. In relatively simple be a regular GET request with an Upgrade offer. In relatively simple
setups with just one IP address and a single server for all traffic setups with just one IP address and a single server for all traffic
skipping to change at page 12, line 13 skipping to change at page 13, line 13
of extensibility. of extensibility.
2. Conformance requirements 2. Conformance requirements
All diagrams, examples, and notes in this specification are non- All diagrams, examples, and notes in this specification are non-
normative, as are all sections explicitly marked non-normative. normative, as are all sections explicitly marked non-normative.
Everything else in this specification is normative. Everything else in this specification is normative.
The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this "RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this
document are to be interpreted as described in RFC2119. For document are to be interpreted as described in RFC2119. [RFC2119]
readability, these words do not appear in all uppercase letters in
this specification. [RFC2119]
Requirements phrased in the imperative as part of algorithms (such as Requirements phrased in the imperative as part of algorithms (such as
"strip any leading space characters" or "return false and abort these "strip any leading space characters" or "return false and abort these
steps") are to be interpreted with the meaning of the key word steps") are to be interpreted with the meaning of the key word
("must", "should", "may", etc) used in introducing the algorithm. ("must", "should", "may", etc) used in introducing the algorithm.
Conformance requirements phrased as algorithms or specific steps may Conformance requirements phrased as algorithms or specific steps MAY
be implemented in any manner, so long as the end result is be implemented in any manner, so long as the end result is
equivalent. (In particular, the algorithms defined in this equivalent. (In particular, the algorithms defined in this
specification are intended to be easy to follow, and not intended to specification are intended to be easy to follow, and not intended to
be performant.) be performant.)
Implementations may impose implementation-specific limits on Implementations MAY impose implementation-specific limits on
otherwise unconstrained inputs, e.g. to prevent denial of service otherwise unconstrained inputs, e.g. to prevent denial of service
attacks, to guard against running out of memory, or to work around attacks, to guard against running out of memory, or to work around
platform-specific limitations. platform-specific limitations.
The conformance classes defined by this specification are user agents The conformance classes defined by this specification are user agents
and servers. and servers.
2.1. Terminology 2.1. Terminology
*ASCII* shall mean the character-encoding scheme defined in *ASCII* shall mean the character-encoding scheme defined in
skipping to change at page 13, line 5 skipping to change at page 13, line 52
range U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL range U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL
LETTER Z). LETTER Z).
Comparing two strings in an *ASCII case-insensitive* manner means Comparing two strings in an *ASCII case-insensitive* manner means
comparing them exactly, code point for code point, except that the comparing them exactly, code point for code point, except that the
characters in the range U+0041 to U+005A (i.e. LATIN CAPITAL LETTER characters in the range U+0041 to U+005A (i.e. LATIN CAPITAL LETTER
A to LATIN CAPITAL LETTER Z) and the corresponding characters in the A to LATIN CAPITAL LETTER Z) and the corresponding characters in the
range U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL range U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL
LETTER Z) are considered to also match. LETTER Z) are considered to also match.
The term "URI" is used in this section in a manner consistent with The term "URI" is used in this document as defined in [RFC3986].
the terminology used in HTML, namely, to denote a string that might
or might not be a valid URI or IRI and to which certain error
handling behaviors will be applied when the string is parsed.
[RFC3986]
When an implementation is required to _send_ data as part of the When an implementation is required to _send_ data as part of the
WebSocket protocol, the implementation may delay the actual WebSocket protocol, the implementation MAY delay the actual
transmission arbitrarily, e.g. buffering data so as to send fewer IP transmission arbitrarily, e.g. buffering data so as to send fewer IP
packets. packets.
3. WebSocket URIs 3. WebSocket URIs
3.1. Parsing WebSocket URIs 3.1. Parsing WebSocket URIs
The steps to *parse a WebSocket URI's components* from a string /uri/ The steps to *parse a WebSocket URI's components* from a string /uri/
are as follows. These steps return either a /host/, a /port/, a are as follows. These steps return either a /host/, a /port/, a
/resource name/, and a /secure/ flag, or they fail. /resource name/, and a /secure/ flag, or they fail.
1. If the /uri/ string is not an absolute URI, then fail this 1. If the /uri/ string is not an absolute URI, then fail this
algorithm. [RFC3986] [RFC3987] algorithm. [RFC3986]
2. Resolve the /uri/ string using the resolve a Web address 2. Resolve the /uri/ string using the resolve a Web address
algorithm defined by the Web addresses specification, with the algorithm defined by the Web addresses specification, with the
URI character encoding set to UTF-8. [RFC3629] [RFC3986] URI character encoding set to UTF-8. [RFC3629] [RFC3986]
[RFC3987] [RFC3987]
NOTE: It doesn't matter what it is resolved relative to, since NOTE: It doesn't matter what it is resolved relative to, since
we already know it is an absolute URI at this point. we already know it is an absolute URI at this point.
3. If /uri/ does not have a <scheme> component whose value, when 3. If /uri/ does not have a <scheme> component whose value, when
converted to ASCII lowercase, is either "ws" or "wss", then fail converted to ASCII lowercase, is either "ws" or "wss", then fail
this algorithm. this algorithm.
4. If /uri/ has a <fragment> component, then fail this algorithm. 4. If /uri/ has a <fragment> component, then fail this algorithm.
5. If the <scheme> component of /uri/ is "ws", set /secure/ to 5. If the <scheme> component of /uri/ is "ws", set /secure/ to
false; otherwise, if the <scheme> component is "wss", set false; otherwise, if the <scheme> component is "wss", set
/secure/ to true; otherwise, fail this algorithm. /secure/ to true; if neither of the above apply, fail this
algorithm.
6. Let /host/ be the value of the <host> component of /uri/, 6. Let /host/ be the value of the <host> component of /uri/,
converted to ASCII lowercase. converted to ASCII lowercase.
7. If /uri/ has a <port> component, then let /port/ be that 7. If /uri/ has a <port> component, then let /port/ be that
component's value; otherwise, there is no explicit /port/. component's value; otherwise, there is no explicit /port/.
8. If there is no explicit /port/, then: if /secure/ is false, let 8. If there is no explicit /port/, then: if /secure/ is false, let
/port/ be 80, otherwise let /port/ be 443. /port/ be 80, otherwise let /port/ be 443.
skipping to change at page 15, line 32 skipping to change at page 16, line 32
5. Append /resource name/ to /uri/. 5. Append /resource name/ to /uri/.
6. Return /uri/. 6. Return /uri/.
3.3. Valid WebSocket URIs 3.3. Valid WebSocket URIs
For a WebSocket URI to be considered valid, the following conditions For a WebSocket URI to be considered valid, the following conditions
MUST hold. MUST hold.
o The /host/ must be ASCII-only (i.e. it must have been punycode- o The /host/ MUST be ASCII-only (i.e. it MUST have been punycode-
encoded already if necessary, and MUST NOT contain any characters encoded [RFC3492] already if necessary, and MUST NOT contain any
above U+007E). characters above U+007E).
o The /resource name/ string must be a non-empty string of o The /resource name/ string MUST be a non-empty string of
characters in the range U+0021 to U+007E that starts with a U+002F characters in the range U+0021 to U+007E and MUST start with a
SOLIDUS character (/). U+002F SOLIDUS character (/).
Any WebSocket URIs not meeting the above criteria are considered Any WebSocket URIs not meeting the above criteria are considered
invalid, and a client MUST NOT attempt to make a connection to an invalid. A client MUST NOT attempt to make a connection to an
invalid WebSocket URI. A client SHOULD attempt to parse a URI invalid WebSocket URI. A client SHOULD attempt to parse a URI
obtained from any external source (such as a web site or a user) obtained from any external source (such as a web site or a user)
using the steps specified in Section 3.1 to obtain a valid WebSocket using the steps specified in Section 3.1 to obtain a valid WebSocket
URI, but MUST NOT attempt to connect with such an unparsed URI, and URI, but MUST NOT attempt to connect with such an unparsed URI, and
instead only use the parsed version and only if that version is instead only use the parsed version and only if that version is
considered valid by the criteria above. considered valid by the criteria above.
4. Data Framing 4. Data Framing
4.1. Overview 4.1. Overview
In the WebSocket protocol, data is transmitted using a sequence of In the WebSocket protocol, data is transmitted using a sequence of
frames. Frames sent from the client to the server are masked to frames. Frames sent from the client to the server are masked to
avoid confusing network intermediaries, such as intercepting proxies. avoid confusing network intermediaries, such as intercepting proxies.
Frames sent from the server to the client are not masked. Frames sent from the server to the client are not masked.
The base framing protocol defines a frame type with an opcode, a The base framing protocol defines a frame type with an opcode, a
payload length, and designated locations for extension and payload length, and designated locations for extension and
application data, which together define the _payload_ data. Certain application data, which together define the _payload_ data. Certain
bits and opcodes are reserved for future expansion of the protocol. bits and opcodes are reserved for future expansion of the protocol.
As such, In the absence of extensions negotiated during the opening As such, in the absence of extensions negotiated during the opening
handshake (Section 5), all reserved bits MUST be 0 and reserved handshake (Section 5), all reserved bits MUST be 0 and reserved
opcode values MUST NOT be used. opcode values MUST NOT be used.
A data frame MAY be transmitted by either the client or the server at A data frame MAY be transmitted by either the client or the server at
any time after handshake completion and before that endpoint has sent any time after handshake completion and before that endpoint has sent
a close message (Section 4.5.1). a close message (Section 4.5.1).
4.2. Client-to-Server Masking 4.2. Base Framing Protocol
The client MUST mask all frames sent to the server.
The masking-key is contained completely within the frame.
The masking-key is a 32-bit value chosen at random by the client.
The masking-key MUST be derived from a strong source of entropy, and
the masking-key for a given frame MUST NOT make it simple for a
server to predict the masking-key for a subsequent frame.
Each masked frame consists of a 32-bit masking-key followed by
masked-data:
masked-frame = masking-key masked-data
masking-key = 4full-octet
masked-data = *full-octet
full-octet = %x00-FF
The masked-data is the clear-text frame "encrypted" using a simple
XOR cipher as follows.
Octet i of the masked-data is the XOR of octet i of the clear text
frame with octet i modulo 4 of the masking-key:
j = i MOD 4
masked-octet-i = clear-text-octet-i XOR octet-j-of-masking-key
When preparing a masked-frame, the client MUST pick a fresh masking-
key uniformly at random from the set of allowed 32-bit values. The
unpredictability of the masking-nonce is essential to prevent the
author of malicious application data from selecting the bytes that
appear on the wire.
4.3. Base Framing Protocol
This wire format for the data transfer part is described by the ABNF This wire format for the data transfer part is described by the ABNF
given in detail in this section. A high level overview of the [RFC5234] given in detail in this section. A high level overview of
framing is given in the following figure. [RFC5234] the framing is given in the following figure.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-------+-+-------------+-------------------------------+ +-+-+-+-+-------+-+-------------+-------------------------------+
|F|R|R|R| opcode|R| Payload len | Extended payload length | |F|R|R|R| opcode|M| Payload len | Extended payload length |
|I|S|S|S| (4) |S| (7) | (16/63) | |I|S|S|S| (4) |A| (7) | (16/63) |
|N|V|V|V| |V| | (if payload len==126/127) | |N|V|V|V| |S| | (if payload len==126/127) |
| |1|2|3| |4| | | | |1|2|3| |K| | |
+-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - + +-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
| Extended payload length continued, if payload len == 127 | | Extended payload length continued, if payload len == 127 |
+ - - - - - - - - - - - - - - - +-------------------------------+ + - - - - - - - - - - - - - - - +-------------------------------+
| | Extension data | | |Masking-key, if MASK set to 1 |
+-------------------------------+ - - - - - - - - - - - - - - - + +-------------------------------+-------------------------------+
: : | Masking-key (continued) | Payload Data |
+---------------------------------------------------------------+ +-------------------------------- - - - - - - - - - - - - - - - +
: Application data : : Payload Data continued ... :
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
| Payload Data continued ... |
+---------------------------------------------------------------+ +---------------------------------------------------------------+
FIN: 1 bit FIN: 1 bit
Indicates that this is the final fragment in a message. The first Indicates that this is the final fragment in a message. The first
fragment may also be the final fragment. fragment MAY also be the final fragment.
RSV1, RSV2, RSV3, RSV4: 1 bit each RSV1, RSV2, RSV3: 1 bit each
Must be 0 unless an extension is negotiated which defines meanings Must be 0 unless an extension is negotiated which defines meanings
for non-zero values for non-zero values
Opcode: 4 bits Opcode: 4 bits
Defines the interpretation of the payload data Defines the interpretation of the payload data
Payload length: 7 bits Mask: 1 bit
Defines whether the payload data is masked. If set to 1, a
masking key is present in Masking-key, and this is used to unmask
the payload data as per Section 4.3. All frames sent from client
to server have this bit set to 1.
Payload length: 7 bits, 7+16 bits, or 7+64 bits
The length of the payload: if 0-125, that is the payload length. The length of the payload: if 0-125, that is the payload length.
If 126, the following 2 bytes interpreted as a 16 bit unsigned If 126, the following 2 bytes interpreted as a 16 bit unsigned
integer are the payload length. If 127, the following 8 bytes integer are the payload length. If 127, the following 8 bytes
interpreted as a 64-bit unsigned integer (the high bit must be 0) interpreted as a 64-bit unsigned integer (the most significant bit
are the payload length. Multibyte length quantities are expressed MUST be 0) are the payload length. Multibyte length quantities
in network byte order. The payload length is the length of the are expressed in network byte order. The payload length is the
Extension data + the length of the Application Data. The length length of the Extension data + the length of the Application data.
of the Extension data may be zero, in which case the Payload The length of the Extension data may be zero, in which case the
length is the length of the Application data. Payload length is the length of the Application data. The length
of this field is always at least 7 bits. If the value of the
first 7 bits is 0-125, the length of this field is 7 bits. If the
value is 126, there exist 16 additional bits with a 16-bit length.
If the value is 127, there exist 64 additional bits with a 63-bit
length (the most significant bit MUST be 0).
Masking-key: 0 or 4 bytes
All frames sent from the client to the server are masked by a 32-
bit value that is contained within the frame. This field is
present if the Mask bit is set to 1, and is absent if the Mask bit
is set to 0. See Section 4.3 for further information on client-
to-server masking.
Payload data: n bytes
The payload data is defined as Extension Data concatenated with
Application Data.
Extension data: n bytes Extension data: n bytes
The extension data is 0 bytes unless there is a reserved op-code The extension data is 0 bytes unless an extension has been
or reserved bit present in the frame which indicates an extension negotiated. Any extension MUST specify the length of the
has been negotiated. Any extension MUST specify the length of the extension data, or how that length may be calculated, and how the
extension data, or how that length may be calculated, and its use extension use MUST be negotiated during the handshake. If
MUST be negotiated during the handshake. If present, the present, the extension data is included in the total payload
extension data is included in the total payload length. length.
Application data: n bytes Application data: n bytes
Arbitrary application data, taking up the remainder of the frame Arbitrary application data, taking up the remainder of the frame
after any extension data. The length of the Application data is after any extension data. The length of the Application data is
equal to the payload length minus the length of the Extension equal to the payload length minus the length of the Extension
data. data.
The base framing protocol is formally defined by the following ABNF The base framing protocol is formally defined by the following ABNF
[RFC5234]: [RFC5234]:
ws-frame = frame-fin ws-frame = frame-fin
frame-rsv1 frame-rsv1
frame-rsv2 frame-rsv2
frame-rsv3 frame-rsv3
frame-opcode frame-opcode
frame-rsv4 frame-masked
frame-length frame-payload-length
frame-extension [ frame-masking-key ]
application-data; frame-payload-data
frame-fin = %x0 ; more frames of this message follow frame-fin = %x0 ; more frames of this message follow
/ %x1 ; final frame of message / %x1 ; final frame of message
frame-rsv1 = %x0 ; 1 bit, must be 0 frame-rsv1 = %x0 ; 1 bit, MUST be 0
frame-rsv2 = %x0 ; 1 bit, must be 0 frame-rsv2 = %x0 ; 1 bit, MUST be 0
frame-rsv3 = %x0 ; 1 bit, must be 0 frame-rsv3 = %x0 ; 1 bit, MUST be 0
frame-opcode = %x0 ; continuation frame frame-opcode = %x0 ; continuation frame
/ %x1 ; connection close / %x1 ; text frame
/ %x2 ; ping / %x2 ; binary frame
/ %x3 ; pong / %3-7 ; reserved for further non-control frames
/ %x4 ; text frame / %x8 ; connection close
/ %x5 ; binary frame / %x9 ; ping
/ %x6-F ; reserved / %xA ; pong
/ %xB-F ; reserved for further control frames
frame-rsv4 = %x0 ; 1 bit, must be 0 frame-masked = %x0 ; frame is not masked, no frame-masking-key
= %x1 ; frame is masked, frame-masking-key present
frame-length = %x00-7D frame-payload-length = %x00-7D
/ %x7E frame-length-16 / %x7E frame-payload-length-16
/ %x7F frame-length-63 / %x7F frame-payload-length-63
frame-length-16 = %x0000-FFFF frame-payload-length-16 = %x0000-FFFF
frame-length-63 = %x0000000000000000-7FFFFFFFFFFFFFFF frame-payload-length-63 = %x0000000000000000-7FFFFFFFFFFFFFFF
frame-extension = *( %x00-FF ) ; to be defined later frame-masking-key = <4>( %0x00-FF ) ; present only if frame-masked is 1
application-data = *( %x00-FF ) frame-payload-data = (frame-masked-extension-data
frame-masked-application-data) ; frame-masked 1
/ (frame-unmasked-extension-data
frame-unmasked-application-data) ; frame-masked 0
frame-masked-extension-data = *( %x00-FF ) ; to be defined later
frame-masked-application-data = *( %x00-FF )
frame-unmasked-extension-data = *( %x00-FF ) ; to be defined later
frame-unmasked-application-data = *( %x00-FF )
4.3. Client-to-Server Masking
The client MUST mask all frames sent to the server. A server MUST
close the connection upon receiving a frame with the MASK bit set to
0. In this case, a server MAY send a close frame with a status code
of 1002 (protocol error) as defined in Section 7.4.1.
A masked frame MUST have the field frame-masked set to 1, as defined
in Section 4.2.
The masking key is contained completely within the frame, as defined
in Section 4.2 as frame-masking-key. It is used to mask the payload
data defined in the same section as frame-payload-data, which
includes extension and application data.
The masking key is a 32-bit value chosen at random by the client.
The masking key MUST be derived from a strong source of entropy, and
the masking key for a given frame MUST NOT make it simple for a
server to predict the masking key for a subsequent frame.
The masking does not affect the length of the payload data. To
convert masked data into unmasked data, or vice versa, the following
algorithm is applied. The same algorithm applies regardless of the
direction of the translation - e.g. the same steps are applied to
mask the data as to unmask the data.
Octet i of the transformed data ("transformed-octet-i") is the XOR of
octet i of the original data ("original-octet-i") with octet i modulo
4 of the masking key ("masking-key-octet-j"):
j = i MOD 4
transformed-octet-i = original-octet-i XOR masking-key-octet-j
When preparing a masked frame, the client MUST pick a fresh masking
key uniformly at random from the set of allowed 32-bit values. The
unpredictability of the masking-nonce is essential to prevent the
author of malicious application data from selecting the bytes that
appear on the wire.
The payload length, indicated in the framing as frame-payload-length,
does NOT include the length of the masking key. It is the length of
the payload data, e.g. the number of bytes following the masking key.
4.4. Fragmentation 4.4. Fragmentation
The primary purpose of fragmentation is to allow sending a message The primary purpose of fragmentation is to allow sending a message
that is of unknown size when the message is started without having to that is of unknown size when the message is started without having to
buffer that message. If messages couldn't be fragmented, then an buffer that message. If messages couldn't be fragmented, then an
endpoint would have to buffer the entire message so its length could endpoint would have to buffer the entire message so its length could
be counted before first byte is sent. With fragmentation, a server be counted before first byte is sent. With fragmentation, a server
or intermediary may choose a reasonable size buffer, and when the or intermediary may choose a reasonable size buffer, and when the
buffer is full write a fragment to the network. buffer is full write a fragment to the network.
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The following rules apply to fragmentation: The following rules apply to fragmentation:
o An unfragmented message consists of a single frame with the FIN o An unfragmented message consists of a single frame with the FIN
bit set and an opcode other than 0. bit set and an opcode other than 0.
o A fragmented message consists of a single frame with the FIN bit o A fragmented message consists of a single frame with the FIN bit
clear and an opcode other than 0, followed by zero or more frames clear and an opcode other than 0, followed by zero or more frames
with the FIN bit clear and the opcode set to 0, and terminated by with the FIN bit clear and the opcode set to 0, and terminated by
a single frame with the FIN bit set and an opcode of 0. Its a single frame with the FIN bit set and an opcode of 0. Its
content is the concatenation of the application data from each of content is the concatenation of the application data (and any
those frames in order. As an example, for a text message sent as extension data that may be present) from each of those frames in
three fragments, the first fragment would have an opcode of 0x4 order. As an example, for a text message sent as three fragments,
and a FIN bit clear, the second fragment would have an opcode of the first fragment would have an opcode of 0x4 and a FIN bit
0x0 and a FIN bit clear, and the third fragment would have an clear, the second fragment would have an opcode of 0x0 and a FIN
opcode of 0x0 and a FIN bit that is set. bit clear, and the third fragment would have an opcode of 0x0 and
a FIN bit that is set.
o Control frames MAY be injected in the middle of a fragmented o Control frames MAY be injected in the middle of a fragmented
message. Control frames themselves MUST NOT be fragmented. _Note: message. Control frames themselves MUST NOT be fragmented.
if control frames could not be interjected, the latency of a ping,
for example, would be very long if behind a large message. As o An endpoint MUST be capable of handling control frames in the
such, an endpoint MUST be capable of handling control frames in middle of a fragmented message.
the middle of a fragmented message._
o _Note: if control frames could not be interjected, the latency of
a ping, for example, would be very long if behind a large message.
Hence, the requirement of handling control frames in the middle of
a fragmented message._
o A sender MAY create fragments of any size for non control o A sender MAY create fragments of any size for non control
messages. messages.
o Clients and servers MUST support receiving both fragmented and o Clients and servers MUST support receiving both fragmented and
unfragmented messages. unfragmented messages.
o An intermediary MAY change the fragmentation of a message if the o As control frames cannot be fragmented, an intermediary MUST NOT
message uses only opcode and reserved bit values known to the attempt to change the fragmentation of a control frame.
intermediary.
o An intermediary MUST NOT change the fragmentation of a message if
any reserved bit values are used and the meaning of these values
is not known to the intermediary.
o An intermediary MUST NOT change the fragmentation of any message
in the context of a connection where extensions have been
negotiated and the intermediary is not aware of the semantics of
the negotiated extensions.
o As a consequence of these rules, all fragments of a message are of o As a consequence of these rules, all fragments of a message are of
the same type, as set by the first fragment's opcode. Since the same type, as set by the first fragment's opcode. Since
Control frames cannot be fragmented, the type for all fragments in Control frames cannot be fragmented, the type for all fragments in
a message MUST be either text or binary, or one of the reserved a message MUST be either text or binary, or one of the reserved
opcodes. opcodes.
4.5. Control Frames 4.5. Control Frames
Control frames have opcodes of 0x01 (Close), 0x02 (Ping), or 0x03 Control frames are identified by opcodes where the most significant
(Pong). Control frames are used to communicate state about the bit of the opcode is 1. Currently defined opcodes for control frames
websocket. Control frames can be interjected in the middle of a include 0x8 (Close), 0x9 (Ping), and 0xA (Pong). Opcodes 0xB-0xF are
fragmented message. reserved for further control frames yet to be defined.
All control frames MUST be 125 bytes or less in length and MUST NOT Control frames are used to communicate state about the websocket.
be fragmented. Control frames can be interjected in the middle of a fragmented
message.
All control frames MUST have a payload length of 125 bytes or less
and MUST NOT be fragmented.
4.5.1. Close 4.5.1. Close
The Close message contains an opcode of 0x01. The Close message contains an opcode of 0x8.
The Close message MAY contain a body (the "application data" portion The Close message MAY contain a body (the "application data" portion
of the frame) that indicates a reason for closing, such as an of the frame) that indicates a reason for closing, such as an
endpoint shutting down, an endpoint having received a message too endpoint shutting down, an endpoint having received a message too
large, or an endpoint having received a message that does not conform large, or an endpoint having received a message that does not conform
to the format expected by the other endpoint. If there is a body, to the format expected by the other endpoint. If there is a body,
the first two bytes of the body MUST be a 2-byte integer (in network the first two bytes of the body MUST be a 2-byte integer (in network
byte order) representing a status code defined in Section 7.4. byte order) representing a status code defined in Section 7.4.
Following the 2-byte integer the body MAY contain UTF-8 encoded data, Following the 2-byte integer the body MAY contain UTF-8 encoded data,
the interpretation of which is not defined by this specification. the interpretation of which is not defined by this specification.
This data is not necessarily human readable, but may be useful for
debugging or passing information relevant to the script that opened
the connection.
The application MUST NOT send any more data messages after sending a The application MUST NOT send any more data frames after sending a
close message. close message.
If an endpoint receives a Close message and that endpoint did not If an endpoint receives a Close message and that endpoint did not
previously send a Close message, the endpoint MUST send a Close previously send a Close message, the endpoint MUST send a Close
message in response. It SHOULD do so as soon as is practical. message in response. It SHOULD do so as soon as is practical.
After both sending and receiving a close message, an endpoint After both sending and receiving a close message, an endpoint
considers the websocket connection closed, and SHOULD close the considers the websocket connection closed, and SHOULD close the
underlying TCP connection. underlying TCP connection.
If a client and server both send a Close message at the same time, If a client and server both send a Close message at the same time,
both endpoints will have sent and received a Close message and should both endpoints will have sent and received a Close message and should
consider the websocket connection closed and close the underlying TCP consider the websocket connection closed and close the underlying TCP
connection. connection.
4.5.2. Ping 4.5.2. Ping
The Ping message contains an opcode of 0x02. The Ping message contains an opcode of 0x9.
Upon receipt of a Ping message, an endpoint MUST send a Pong message Upon receipt of a Ping message, an endpoint MUST send a Pong message
in response. It SHOULD do so as soon as is practical. The message in response. It SHOULD do so as soon as is practical. The message
bodies of the Ping and Pong MUST be the same. bodies (i.e. both the Extension data (if any) and the Application
data) of the Ping and Pong MUST be the same.
An endpoint MAY send a Ping message any time after the connection is
established and before the connection is closed. NOTE: A ping
message may serve either as a keepalive, or to verify that the remote
endpoint is still responsive.
4.5.3. Pong 4.5.3. Pong
The Pong message contains an opcode of 0x03. The Pong message contains an opcode of 0xA.
Upon receipt of a Ping message, an endpoint MUST send a Pong message Upon receipt of a Ping message, an endpoint MUST send a Pong message
in response. It SHOULD do so as soon as is practical. The message in response. It SHOULD do so as soon as is practical. The message
bodies of the Ping and Pong MUST be the same. A Pong is issued only bodies (i.e. both the Extension data (if any) and the Application
in response to the most recent Ping. data) of the Ping and Pong MUST be the same. In the case multiple
Pings have been received, a Pong MUST be issued only in response to
the most recent Ping.
A Pong message MAY be sent unsolicited. This serves as a
unidirectional heartbeat. A response to an unsolicited pong is not
expected.
4.6. Data Frames 4.6. Data Frames
All frame types not listed in Section 4.5 are data frames, which Data frames (e.g. non control frames) are identified by opcodes where
transport application-layer data. The opcode determines the the most significant bit of the opcode is 0. Currently defined
interpretation of the application data: opcodes for data frames include 0x1 (Text), 0x2 (Binary). Opcodes
0x3-0x7 are reserved for further non-control frames yet to be
defined.
Data frames carry application-layer or extension-layer data. The
opcode determines the interpretation of the data:
Text Text
The payload data is text data encoded as UTF-8. The payload data is text data encoded as UTF-8.
Binary Binary
The payload data is arbitrary binary data whose interpretation is The payload data is arbitrary binary data whose interpretation is
solely up to the application layer. solely up to the application layer.
4.7. Examples 4.7. Examples
_This section is non-normative._ _This section is non-normative._
o A single-frame text message o A single-frame unmasked text message
* 0x84 0x05 0x48 0x65 0x6c 0x6c 0x6f (contains "Hello") * 0x81 0x05 0x48 0x65 0x6c 0x6c 0x6f (contains "Hello")
o A fragmented text message o A single-frame masked text message
* 0x04 0x03 0x48 0x65 0x6c (contains "Hel") * 0x81 0x85 0x37 0xfa 0x21 0x3d 0x7f 0x9f 0x4d 0x51 0x58
(contains "Hello")
o A fragmented unmasked text message
* 0x01 0x03 0x48 0x65 0x6c (contains "Hel")
* 0x80 0x02 0x6c 0x6f (contains "lo") * 0x80 0x02 0x6c 0x6f (contains "lo")
o Ping request and response o Ping request and response
* 0x82 0x05 0x48 0x65 0x6c 0x6c 0x6f (contains a body of "Hello", * 0x89 0x05 0x48 0x65 0x6c 0x6c 0x6f (contains a body of "Hello",
but the contents of the body are arbitrary) but the contents of the body are arbitrary)
* 0x83 0x05 0x48 0x65 0x6c 0x6c 0x6f (contains a body of "Hello", * 0x8a 0x05 0x48 0x65 0x6c 0x6c 0x6f (contains a body of "Hello",
matching the body of the ping) matching the body of the ping)
o 256 bytes binary message in a single frame o 256 bytes binary message in a single unmasked frame
* 0x85 0x7E 0x0100 [256 bytes of binary data] * 0x82 0x7E 0x0100 [256 bytes of binary data]
o 64KiB binary message in a single frame o 64KiB binary message in a single unmasked frame
* 0x85 0x7F 0x0000000000010000 [65536 bytes of binary data] * 0x82 0x7F 0x0000000000010000 [65536 bytes of binary data]
4.8. Extensibility 4.8. Extensibility
The protocol is designed to allow for extensions, which will add The protocol is designed to allow for extensions, which will add
capabilities to the base protocols. The endpoints of a connection capabilities to the base protocols. The endpoints of a connection
MUST negotiate the use of any extensions during the handshake. This MUST negotiate the use of any extensions during the handshake. This
specification provides opcodes 0x6 through 0xF, the extension data specification provides opcodes 0x3 through 0x7 and 0xB through 0xF,
field, and the frame-rsv1, frame-rsv2, frame-rsv3, and frame-rsv4 the extension data field, and the frame-rsv1, frame-rsv2, and frame-
bits of the frame header for use by extensions. The negotiation of rsv3 bits of the frame header for use by extensions. The negotiation
extensions is discussed in further detail in Section 8.1. Below are of extensions is discussed in further detail in Section 8.1. Below
some anticipated uses of extensions. This list is neither complete are some anticipated uses of extensions. This list is neither
nor proscriptive. complete nor proscriptive.
o Extension data may be placed in the payload before the application o Extension data may be placed in the payload before the application
data. data.
o Reserved bits can be allocated for per-frame needs. o Reserved bits can be allocated for per-frame needs.
o Reserved opcode values can be defined. o Reserved opcode values can be defined.
o Reserved bits can be allocated to the opcode field if more opcode o Reserved bits can be allocated to the opcode field if more opcode
values are needed. values are needed.
skipping to change at page 24, line 15 skipping to change at page 27, line 15
5. Opening Handshake 5. Opening Handshake
5.1. Client Requirements 5.1. Client Requirements
User agents running in controlled environments, e.g. browsers on User agents running in controlled environments, e.g. browsers on
mobile handsets tied to specific carriers, may offload the management mobile handsets tied to specific carriers, may offload the management
of the connection to another agent on the network. In such a of the connection to another agent on the network. In such a
situation, the user agent for the purposes of conformance is situation, the user agent for the purposes of conformance is
considered to include both the handset software and any such agents. considered to include both the handset software and any such agents.
When the user agent is to *establish a WebSocket connection* to a When the user agent is to *establish a WebSocket connection* given
WebSocket URI /uri/, it must meet the following requirements. In the either a WebSocket URI /uri/ or the constituent components of a URI
following text, we will use terms from Section 3 such as "/host/" and as specified in Section 11, it MUST meet the following requirements.
"/secure/ flag" as defined in that section. In the following text, we will use terms from Section 3 such as
"/host/" and "/secure/ flag" as defined in that section.
1. The WebSocket URI and its components MUST be valid according to 1. The WebSocket URI and its components derived by applying the
steps defined in Section 3.3, or if the following algorithm was
supplied with the constituent components as defined in Section 11
then those components provided, MUST be valid according to
Section 3.3. If any of the requirements are not met, the client Section 3.3. If any of the requirements are not met, the client
MUST fail the WebSocket connection and abort these steps. MUST fail the WebSocket connection and abort these steps.
2. If the user agent already has a WebSocket connection to the 2. If the user agent already has a WebSocket connection to the
remote host (IP address) identified by /host/, even if known by remote host (IP address) identified by /host/ and port /port/
another name, the user agent MUST wait until that connection has pair, even if the remote host is known by another name, the user
been established or for that connection to have failed. There agent MUST wait until that connection has been established or for
MUST be no more than one connection in a CONNECTING state. If that connection to have failed. There MUST be no more than one
multiple connections to the same IP address are attempted connection in a CONNECTING state. If multiple connections to the
simultaneously, the user agent MUST serialize them so that there same IP address are attempted simultaneously, the user agent MUST
is no more than one connection at a time running through the serialize them so that there is no more than one connection at a
following steps. time running through the following steps.
If the user agent cannot determine the IP address of the remote If the user agent cannot determine the IP address of the remote
host (for example because all communication is being done through host (for example because all communication is being done through
a proxy server that performs DNS queries itself), then the user a proxy server that performs DNS queries itself), then the user
agent MUST assume for the purposes of this step that each host agent MUST assume for the purposes of this step that each host
name refers to a distinct remote host, but should instead limit name refers to a distinct remote host, but should instead limit
the total number of simultaneous connections that are not the total number of simultaneous connections that are not
established to a reasonably low number (e.g., in a Web browser, established to a reasonably low number (e.g., in a Web browser,
to the number of tabs the user has open). to the number of tabs the user has open).
NOTE: This makes it harder for a script to perform a denial of NOTE: This makes it harder for a script to perform a denial of
service attack by just opening a large number of WebSocket service attack by just opening a large number of WebSocket
connections to a remote host. A server can further reduce the connections to a remote host. A server can further reduce the
load on itself when attacked by making use of this by pausing load on itself when attacked by making use of this by pausing
before closing the connection, as that will reduce the rate at before closing the connection, as that will reduce the rate at
which the client reconnects. which the client reconnects.
NOTE: There is no limit to the number of established WebSocket NOTE: There is no limit to the number of established WebSocket
connections a user agent can have with a single remote host. connections a user agent can have with a single remote host.
Servers can refuse to connect users with an excessive number of Servers can refuse to accept connections from hosts with an
connections, or disconnect resource-hogging users when suffering excessive number of existing connections, or disconnect resource-
high load. hogging connections when suffering high load.
3. _Proxy Usage_: If the user agent is configured to use a proxy 3. _Proxy Usage_: If the user agent is configured to use a proxy
when using the WebSocket protocol to connect to host /host/ when using the WebSocket protocol to connect to host /host/
and/or port /port/, then the user agent SHOULD connect to that and/or port /port/, then the user agent SHOULD connect to that
proxy and ask it to open a TCP connection to the host given by proxy and ask it to open a TCP connection to the host given by
/host/ and the port given by /port/. /host/ and the port given by /port/.
EXAMPLE: For example, if the user agent uses an HTTP proxy for EXAMPLE: For example, if the user agent uses an HTTP proxy for
all traffic, then if it was to try to connect to port 80 on all traffic, then if it was to try to connect to port 80 on
server example.com, it might send the following lines to the server example.com, it might send the following lines to the
skipping to change at page 25, line 39 skipping to change at page 28, line 43
the port given by /port/. the port given by /port/.
NOTE: Implementations that do not expose explicit UI for NOTE: Implementations that do not expose explicit UI for
selecting a proxy for WebSocket connections separate from other selecting a proxy for WebSocket connections separate from other
proxies are encouraged to use a SOCKS proxy for WebSocket proxies are encouraged to use a SOCKS proxy for WebSocket
connections, if available, or failing that, to prefer the proxy connections, if available, or failing that, to prefer the proxy
configured for HTTPS connections over the proxy configured for configured for HTTPS connections over the proxy configured for
HTTP connections. HTTP connections.
For the purpose of proxy autoconfiguration scripts, the URI to For the purpose of proxy autoconfiguration scripts, the URI to
pass the function must be constructed from /host/, /port/, pass the function MUST be constructed from /host/, /port/,
/resource name/, and the /secure/ flag using the steps to /resource name/, and the /secure/ flag using the steps to
construct a WebSocket URI. construct a WebSocket URI as given in Section 3.2.
NOTE: The WebSocket protocol can be identified in proxy NOTE: The WebSocket protocol can be identified in proxy
autoconfiguration scripts from the scheme ("ws:" for unencrypted autoconfiguration scripts from the scheme ("ws:" for unencrypted
connections and "wss:" for encrypted connections). connections and "wss:" for encrypted connections).
4. If the connection could not be opened, either because a direct 4. If the connection could not be opened, either because a direct
connection failed or because any proxy used returned an error, connection failed or because any proxy used returned an error,
then the user agent MUST fail the WebSocket connection and abort then the user agent MUST fail the WebSocket connection and abort
the connection attempt. the connection attempt.
5. If /secure/ is true, the user agent MUST perform a TLS handshake 5. If /secure/ is true, the user agent MUST perform a TLS handshake
over the connection. If this fails (e.g. the server's over the connection [RFC2818]. If this fails (e.g. the server's
certificate could not be verified), then the user agent MUST fail certificate could not be verified), then the user agent MUST fail
the WebSocket connection and abort the connection. Otherwise, the WebSocket connection and abort the connection. Otherwise,
all further communication on this channel MUST run through the all further communication on this channel MUST run through the
encrypted tunnel. [RFC2246] encrypted tunnel. [RFC5246]
User agents MUST use the Server Name Indication extension in the User agents MUST use the Server Name Indication extension in the
TLS handshake. [RFC4366] TLS handshake. [RFC6066]
Once a connection to the server has been established (including a Once a connection to the server has been established (including a
connection via a proxy or over a TLS-encrypted tunnel), the client connection via a proxy or over a TLS-encrypted tunnel), the client
MUST send a handshake to the server. The handshake consists of an MUST send a handshake to the server. The handshake consists of an
HTTP upgrade request, along with a list of required and optional HTTP upgrade request, along with a list of required and optional
headers. The requirements for this handshake are as follows. headers. The requirements for this handshake are as follows.
1. The handshake must be a valid HTTP request as specified by 1. The handshake MUST be a valid HTTP request as specified by
[RFC2616]. [RFC2616].
2. The Method of the request MUST be GET and the HTTP version MUST 2. The Method of the request MUST be GET and the HTTP version MUST
be at least 1.1. be at least 1.1.
For example, if the WebSocket URI is "ws://example.com/chat", For example, if the WebSocket URI is "ws://example.com/chat",
The first line sent SHOULD be "GET /chat HTTP/1.1" The first line sent should be "GET /chat HTTP/1.1"
3. The request must contain a "Request-URI" as part of the GET 3. The request MUST contain a "Request-URI" as part of the GET
method. This MUST match the /resource name/ Section 3. method. This MUST match the /resource name/ Section 3.
4. The request MUST contain a "Host" header whose value is equal to 4. The request MUST contain a "Host" header whose value is equal to
the authority component of the WebSocket URI. /host/
5. The request MUST contain an "Upgrade" header whose value is 5. The request MUST contain an "Upgrade" header whose value is
equal to "websocket". equal to "websocket".
6. The request MUST contain a "Connection" header whose value MUST 6. The request MUST contain a "Connection" header whose value MUST
include the "Upgrade" token. include the "Upgrade" token.
7. The request MUST include a header with the name "Sec-WebSocket- 7. The request MUST include a header with the name "Sec-WebSocket-
Key". The value of this header MUST be a nonce consisting of a Key". The value of this header MUST be a nonce consisting of a
randomly selected 16-byte value that has been base64-encoded randomly selected 16-byte value that has been base64-encoded
[RFC3548]. The nonce MUST be randomly selected randomly for [RFC3548]. The nonce MUST be selected randomly for each
each connection. connection.
NOTE: As an example, if the randomly selected value was the NOTE: As an example, if the randomly selected value was the
sequence of bytes 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 sequence of bytes 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09
0x0a 0x0b 0x0c 0x0d 0x0e 0x0f 0x10, the value of the header 0x0a 0x0b 0x0c 0x0d 0x0e 0x0f 0x10, the value of the header
would be "AQIDBAUGBwgJCgsMDQ4PEC==" would be "AQIDBAUGBwgJCgsMDQ4PEC=="
8. The request MUST include a header with the name "Sec-WebSocket- 8. The request MUST include a header with the name "Sec-WebSocket-
Origin" if the request is coming from a browser client. If the Origin" if the request is coming from a browser client. If the
connection is from a non-browser client, the request MAY include connection is from a non-browser client, the request MAY include
this header if the semantics of that client match the use-case this header if the semantics of that client match the use-case
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which the code establishing the connection is running, and MUST which the code establishing the connection is running, and MUST
be lower-case. The value MUST NOT contain letters in the range be lower-case. The value MUST NOT contain letters in the range
U+0041 to U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL U+0041 to U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL
LETTER Z) [I-D.ietf-websec-origin]. LETTER Z) [I-D.ietf-websec-origin].
As an example, if code is running on www.example.com attempting As an example, if code is running on www.example.com attempting
to establish a connection to ww2.example.com, the value of the to establish a connection to ww2.example.com, the value of the
header would be "http://www.example.com". header would be "http://www.example.com".
9. The request MUST include a header with the name "Sec-WebSocket- 9. The request MUST include a header with the name "Sec-WebSocket-
Version". The value of this header must be 6. Version". The value of this header MUST be 7.
10. The request MAY include a header with the name "Sec-WebSocket- 10. The request MAY include a header with the name "Sec-WebSocket-
Protocol". If present, this value indicates the subprotocol(s) Protocol". If present, this value indicates the subprotocol(s)
the client wishes to speak. The elements that comprise this the client wishes to speak. The elements that comprise this
value MUST be non-empty strings with characters in the range value MUST be non-empty strings with characters in the range
U+0021 to U+007E and MUST all be unique. The ABNF for the value U+0021 to U+007E and MUST all be unique strings. The ABNF for
of this header is 1#(token | quoted-string), where the the value of this header is 1#(token | quoted-string), where the
definitions of constructs and rules are as given in [RFC2616]. definitions of constructs and rules are as given in [RFC2616].
11. The request MAY include a header with the name "Sec-WebSocket- 11. The request MAY include a header with the name "Sec-WebSocket-
Extensions". If present, this value indicates the protocol- Extensions". If present, this value indicates the protocol-
level extension(s) the client wishes to speak. The level extension(s) the client wishes to speak. The
interpretation and format of this header is described in interpretation and format of this header is described in
Section 8.1. Section 8.1.
12. The request MAY include headers associated with sending cookies, 12. The request MAY include headers associated with sending cookies,
as defined by the appropriate specifications as defined by the appropriate specifications
[I-D.ietf-httpstate-cookie]. [I-D.ietf-httpstate-cookie].
Once the client's opening handshake has been sent, the client MUST Once the client's opening handshake has been sent, the client MUST
wait for a response from the server before sending any further data. wait for a response from the server before sending any further data.
The client MUST validate the server's response as follows: The client MUST validate the server's response as follows:
o If the status code received from the server is not 101, the client o If the status code received from the server is not 101, the client
MUST fail the WebSocket connection. handles the response per HTTP procedures. Otherwise, proceed as
follows.
o If the response lacks an Upgrade header or the Upgrade header o If the response lacks an Upgrade header or the Upgrade header
contains a value that is not an ASCII case-insensitive match for contains a value that is not an ASCII case-insensitive match for
the value "websocket", the client MUST fail the WebSocket the value "websocket", the client MUST fail the WebSocket
connection. connection.
o If the response lacks a Connection header or the Connection header o If the response lacks a Connection header or the Connection header
contains a value that is not an ASCII case-insensitive match for contains a value that is not an ASCII case-insensitive match for
the value "Upgrade", the client MUST fail the WebSocket the value "Upgrade", the client MUST fail the WebSocket
connection. connection.
o If the response lacks a Sec-WebSocket-Accept header or the Sec- o If the response lacks a Sec-WebSocket-Accept header or the Sec-
WebSocket-Accept contains a value other than the base64-encoded WebSocket-Accept contains a value other than the base64-encoded
SHA-1 of the concatenation of the Sec-WebSocket-Key (as a string, SHA-1 of the concatenation of the Sec-WebSocket-Key (as a string,
not base64-decoded) with the string "258EAFA5-E914-47DA-95CA- not base64-decoded) with the string "258EAFA5-E914-47DA-95CA-
C5AB0DC85B11", the client MUST fail the WebSocket connection. C5AB0DC85B11", the client MUST fail the WebSocket connection.
Where the algorithm above requires that a user agent fail the Where the algorithm above requires that a user agent fail the
WebSocket connection, the user agent may first read an arbitrary WebSocket connection, the user agent MAY first read an arbitrary
number of further bytes from the connection (and then discard them) number of further bytes from the connection (and then discard them)
before actually *failing the WebSocket connection*. Similarly, if a before actually *failing the WebSocket connection*. Similarly, if a
user agent can show that the bytes read from the connection so far user agent can show that the bytes read from the connection so far
are such that there is no subsequent sequence of bytes that the are such that there is no subsequent sequence of bytes that the
server can send that would not result in the user agent being server can send that would not result in the user agent being
required to *fail the WebSocket connection*, the user agent may required to *fail the WebSocket connection*, the user agent MAY
immediately *fail the WebSocket connection* without waiting for those immediately *fail the WebSocket connection* without waiting for those
bytes. bytes.
NOTE: The previous paragraph is intended to make it conforming for NOTE: The previous paragraph is intended to make it conforming for
user agents to implement the algorithm in subtly different ways that user agents to implement the algorithm in subtly different ways that
are equivalent in all ways except that they terminate the connection are equivalent in all ways except that they terminate the connection
at earlier or later points. For example, it enables an at earlier or later points. For example, it enables an
implementation to buffer the entire handshake response before implementation to buffer the entire handshake response before
checking it, or to verify each field as it is received rather than checking it, or to verify each field as it is received rather than
collecting all the fields and then checking them as a block. collecting all the fields and then checking them as a block.
5.2. Server-side requirements 5.2. Server-side requirements
_This section only applies to servers._ _This section only applies to servers._
Servers may offload the management of the connection to other agents Servers MAY offload the management of the connection to other agents
on the network, for example load balancers and reverse proxies. In on the network, for example load balancers and reverse proxies. In
such a situation, the server for the purposes of conformance is such a situation, the server for the purposes of conformance is
considered to include all parts of the server-side infrastructure considered to include all parts of the server-side infrastructure
from the first device to terminate the TCP connection all the way to from the first device to terminate the TCP connection all the way to
the server that processes requests and sends responses. the server that processes requests and sends responses.
EXAMPLE: For example, a data center might have a server that responds EXAMPLE: For example, a data center might have a server that responds
to WebSocket requests with an appropriate handshake, and then passes to WebSocket requests with an appropriate handshake, and then passes
the connection to another server to actually process the data frames. the connection to another server to actually process the data frames.
For the purposes of this specification, the "server" is the For the purposes of this specification, the "server" is the
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5.2.1. Reading the client's opening handshake 5.2.1. Reading the client's opening handshake
When a client starts a WebSocket connection, it sends its part of the When a client starts a WebSocket connection, it sends its part of the
opening handshake. The server must parse at least part of this opening handshake. The server must parse at least part of this
handshake in order to obtain the necessary information to generate handshake in order to obtain the necessary information to generate
the server part of the handshake. the server part of the handshake.
The client handshake consists of the following parts. If the server, The client handshake consists of the following parts. If the server,
while reading the handshake, finds that the client did not send a while reading the handshake, finds that the client did not send a
handshake that matches the description below, the server must abort handshake that matches the description below, the server MUST abort
the WebSocket connection. the WebSocket connection.
1. An HTTP/1.1 or higher GET request, including a "Request-URI" 1. An HTTP/1.1 or higher GET request, including a "Request-URI"
[RFC2616] that should be interpreted as a /resource name/ [RFC2616] that should be interpreted as a /resource name/
Section 3. Section 3.
2. A "Host" header containing the server's authority. 2. A "Host" header containing the server's authority.
3. A "Sec-WebSocket-Key" header with a base64-encoded value that, 3. A "Sec-WebSocket-Key" header with a base64-encoded value that,
when decoded, is 16 bytes in length. when decoded, is 16 bytes in length.
4. A "Sec-WebSocket-Version" header, with a value of 6. 4. A "Sec-WebSocket-Version" header, with a value of 7.
5. Optionally, a "Sec-WebSocket-Origin" header. This header is sent 5. Optionally, a "Sec-WebSocket-Origin" header. This header is sent
by all browser clients. A connection attempt lacking this header by all browser clients. A connection attempt lacking this header
SHOULD NOT be interpreted as coming from a browser client. SHOULD NOT be interpreted as coming from a browser client.
6. Optionally, a "Sec-WebSocket-Protocol header, with a list of 6. Optionally, a "Sec-WebSocket-Protocol" header, with a list of
values indicating which protocols the client would like to speak, values indicating which protocols the client would like to speak,
ordered by preference. ordered by preference.
7. Optionally, a "Sec-WebSocket-Extensions" header, with a list of 7. Optionally, a "Sec-WebSocket-Extensions" header, with a list of
values indicating which extensions the client would like to values indicating which extensions the client would like to
speak. The interpretation of this header is discussed in speak. The interpretation of this header is discussed in
Section 8.1. Section 8.1.
8. Optionally, other headers, such as those used to send cookies to 8. Optionally, other headers, such as those used to send cookies to
a server. Unknown headers MUST be ignored. a server. Unknown headers MUST be ignored.
5.2.2. Sending the server's opening handshake 5.2.2. Sending the server's opening handshake
When a client establishes a WebSocket connection to a server, the When a client establishes a WebSocket connection to a server, the
server must complete the following steps to accept the connection and server MUST complete the following steps to accept the connection and
send the server's opening handshake. send the server's opening handshake.
1. If the server supports encryption, perform a TLS handshake over 1. If the server supports encryption, perform a TLS handshake over
the connection. If this fails (e.g. the client indicated a host the connection. If this fails (e.g. the client indicated a host
name in the extended client hello "server_name" extension that name in the extended client hello "server_name" extension that
the server does not host), then close the connection; otherwise, the server does not host), then close the connection; otherwise,
all further communication for the connection (including the all further communication for the connection (including the
server handshake) must run through the encrypted tunnel. server handshake) MUST run through the encrypted tunnel.
[RFC2246] [RFC5246]
2. Establish the following information: 2. Establish the following information:
/origin/ /origin/
The |Sec-WebSocket-Origin| header in the client's handshake The |Sec-WebSocket-Origin| header in the client's handshake
indicates the origin of the script establishing the indicates the origin of the script establishing the
connection. The origin is serialized to ASCII and converted connection. The origin is serialized to ASCII and converted
to lowercase. The server MAY use this information as part of to lowercase. The server MAY use this information as part of
a determination of whether to accept the incoming connection. a determination of whether to accept the incoming connection.
If the server does not validate the origin, it will accept
connections from anywhere. For more detail, refer to
Section 9.
/key/ /key/
The |Sec-WebSocket-Key| header in the client's handshake The |Sec-WebSocket-Key| header in the client's handshake
includes a base64-encoded value that, if decoded, is 16 bytes includes a base64-encoded value that, if decoded, is 16 bytes
in length. This (encoded) value is used in the creation of in length. This (encoded) value is used in the creation of
the server's handshake to indicate an acceptance of the the server's handshake to indicate an acceptance of the
connection. It is not necessary for the server to base64- connection. It is not necessary for the server to base64-
decode the Sec-WebSocket-Key value. decode the Sec-WebSocket-Key value.
/version/ /version/
The |Sec-WebSocket-Version| header in the client's handshake The |Sec-WebSocket-Version| header in the client's handshake
includes the version of the WebSocket protocol the client is includes the version of the WebSocket protocol the client is
attempting to communicate with. If this version does not attempting to communicate with. If this version does not
match a version understood by the server, the server MUST match a version understood by the server, the server MUST
abort the WebSocket connection. The server MAY send a non-200 abort the WebSocket connection. The server MAY send a non-200
response code with a |Sec-WebSocket-Version| header indicating response code with a |Sec-WebSocket-Version| header indicating
the version(s) the server is capable of understanding along the version(s) the server is capable of understanding.
with this non-200 response code.
/resource name/ /resource name/
An identifier for the service provided by the server. If the An identifier for the service provided by the server. If the
server provides multiple services, then the value should be server provides multiple services, then the value should be
derived from the resource name given in the client's handshake derived from the resource name given in the client's handshake
from the Request-URI [RFC2616] of the GET method. from the Request-URI [RFC2616] of the GET method.
/subprotocol/ /subprotocol/
A (possibly empty) list representing the subprotocol the Either a single value or null, representing the subprotocol
server is ready to use. If the server supports multiple the server is ready to use. If the server supports multiple
subprotocols, then the value should be derived from the subprotocols, then the value MUST be derived from the client's
client's handshake, specifically by selecting one of the handshake, specifically by selecting one of the values from
values from the "Sec-WebSocket-Protocol" field. The absence the "Sec-WebSocket-Protocol" field. The absence of such a
of such a field is equivalent to the null value. The empty field is equivalent to the null value. The empty string is
string is not the same as the null value for these purposes. not the same as the null value for these purposes, and is not
a legal value for this field. The ABNF for the value of this
header is (token | quoted-string), where the definitions of
constructs and rules are as given in [RFC2616].
/extensions/ /extensions/
A (possibly empty) list representing the protocol-level A (possibly empty) list representing the protocol-level
extensions the server is ready to use. If the server supports extensions the server is ready to use. If the server supports
multiple extensions, then the value should be derived from the multiple extensions, then the value MUST be derived from the
client's handshake, specifically by selecting one or more of client's handshake, specifically by selecting one or more of
the values from the "Sec-WebSocket-Extensions" field. The the values from the "Sec-WebSocket-Extensions" field. The
absence of such a field is equivalent to the null value. The absence of such a field is equivalent to the null value. The
empty string is not the same as the null value for these empty string is not the same as the null value for these
purposes. Extensions not listed by the client MUST NOT be purposes. Extensions not listed by the client MUST NOT be
listed. The method by which these values should be selected listed. The method by which these values should be selected
and interpreted is discussed in Section 8.1. and interpreted is discussed in Section 8.1.
3. If the server chooses to accept the incoming connection, it must 3. If the server chooses to accept the incoming connection, it MUST
reply with a valid HTTP response indicating the following. reply with a valid HTTP response indicating the following.
1. A 101 response code. Such a response could look like 1. A 101 response code. Such a response could look like
"HTTP/1.1 101 Switching Protocols" "HTTP/1.1 101 Switching Protocols"
2. A "Sec-WebSocket-Accept" header. The value of this header is 2. A "Sec-WebSocket-Accept" header. The value of this header is
constructed by concatenating /key/, defined above in constructed by concatenating /key/, defined above in
Paragraph 2 of Section 5.2.2, with the string "258EAFA5-E914- Paragraph 2 of Section 5.2.2, with the string "258EAFA5-E914-
47DA-95CA-C5AB0DC85B11", taking the SHA-1 hash of this 47DA-95CA-C5AB0DC85B11", taking the SHA-1 hash of this
concatenated value to obtain a 20-byte value, and base64- concatenated value to obtain a 20-byte value, and base64-
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3. Optionally, a "Sec-WebSocket-Protocol" header, with a value 3. Optionally, a "Sec-WebSocket-Protocol" header, with a value
/subprotocol/ as defined in Paragraph 2 of Section 5.2.2. /subprotocol/ as defined in Paragraph 2 of Section 5.2.2.
4. Optionally, a "Sec-WebSocket-Extensions" header, with a value 4. Optionally, a "Sec-WebSocket-Extensions" header, with a value
/extensions/ as defined in Paragraph 2 of Section 5.2.2. /extensions/ as defined in Paragraph 2 of Section 5.2.2.
This completes the server's handshake. If the server finishes these This completes the server's handshake. If the server finishes these
steps without aborting the WebSocket connection, and if the client steps without aborting the WebSocket connection, and if the client
does not then fail the WebSocket connection, then the connection is does not then fail the WebSocket connection, then the connection is
established and the server may begin sending and receiving data, as established and the server may begin sending and receiving data.
described in the next section.
6. Error Handling 6. Error Handling
6.1. Handling errors in UTF-8 from the server 6.1. Handling errors in UTF-8 from the server
When a client is to interpret a byte stream as UTF-8 but finds that When a client is to interpret a byte stream as UTF-8 but finds that
the byte stream is not in fact a valid UTF-8 stream, then any bytes the byte stream is not in fact a valid UTF-8 stream, then any bytes
or sequences of bytes that are not valid UTF-8 sequences must be or sequences of bytes that are not valid UTF-8 sequences MUST be
interpreted as a U+FFFD REPLACEMENT CHARACTER. interpreted as a U+FFFD REPLACEMENT CHARACTER.
6.2. Handling errors in UTF-8 from the client 6.2. Handling errors in UTF-8 from the client
When a server is to interpret a byte stream as UTF-8 but finds that When a server is to interpret a byte stream as UTF-8 but finds that
the byte stream is not in fact a valid UTF-8 stream, behavior is the byte stream is not in fact a valid UTF-8 stream, behavior is
undefined. A server could close the connection, convert invalid byte undefined. A server could close the connection, convert invalid byte
sequences to U+FFFD REPLACEMENT CHARACTERs, store the data verbatim, sequences to U+FFFD REPLACEMENT CHARACTERs, store the data verbatim,
or perform application-specific processing. Subprotocols layered on or perform application-specific processing. Subprotocols layered on
the WebSocket protocol might define specific behavior for servers. the WebSocket protocol might define specific behavior for servers.
7. Closing the connection 7. Closing the connection
7.1. Definitions 7.1. Definitions
7.1.1. Close the WebSocket Connection 7.1.1. Close the WebSocket Connection
To _Close the WebSocket Connection_, an endpoint closes the To _Close the WebSocket Connection_, an endpoint closes the
underlying TCP connection. An endpoint SHOULD use a method that underlying TCP connection. An endpoint SHOULD use a method that
cleanly closes the TCP connection, discarding any trailing bytes that cleanly closes the TCP connection, as well as the TLS session, if
may be received. And endpoint MAY close the connection via any means applicable, discarding any trailing bytes that may be received. An
available when necessary, such as when under attack. endpoint MAY close the connection via any means available when
necessary, such as when under attack.
As an example of how to obtain a clean closure in C using Berkeley As an example of how to obtain a clean closure in C using Berkeley
sockets, one would call shutdown() with SHUT_WR on the socket, call sockets, one would call shutdown() with SHUT_WR on the socket, call
recv() until obtaining a return value of 0 indicating that the peer recv() until obtaining a return value of 0 indicating that the peer
has also performed an orderly shutdown, and finally calling close() has also performed an orderly shutdown, and finally calling close()
on the socket. on the socket.
7.1.2. Start the WebSocket Closing Handshake 7.1.2. Start the WebSocket Closing Handshake
To _start the WebSocket closing handshake_, and endpoint MUST send a To _start the WebSocket closing handshake_, an endpoint MUST send a
Close control frame, as described in Section 4.5.1. Upon receiving a Close control frame, as described in Section 4.5.1. Once an endpoint
Close control frame, the other party sends a Close control frame in has both sent and received a Close control frame, that endpoint
response. Once an endpoint has both sent and received a Close SHOULD _Close the WebSocket Connection_ as defined in Section 7.1.1.
control frame, that endpoint should _Close the WebSocket Connection_
as defined in Section 7.1.1.
7.1.3. The WebSocket Connection Is Closed 7.1.3. The WebSocket Connection Is Closed
When the underlying TCP connection is closed, it is said that _the When the underlying TCP connection is closed, it is said that _the
WebSocket connection is closed_. If the tcp connection was closed WebSocket connection is closed_. If the tcp connection was closed
after the WebSocket closing handshake was completed, the WebSocket after the WebSocket closing handshake was completed, the WebSocket
connection is said to have been closed _cleanly_. connection is said to have been closed _cleanly_.
7.1.4. Fail the WebSocket Connection 7.1.4. Fail the WebSocket Connection
Certain algorithms and specifications require a user agent to _fail Certain algorithms and specifications require a user agent to _fail
the WebSocket connection_. To do so, the user agent must _Close the the WebSocket connection_. To do so, the user agent MUST _Close the
WebSocket Connection_, and MAY report the problem to the user (which WebSocket Connection_, and MAY report the problem to the user (which
would be especially useful for developers) in an appropriate manner. would be especially useful for developers) in an appropriate manner.
Except as indicated above or as specified by the application layer Except as indicated above or as specified by the application layer
(e.g. a script using the WebSocket API), user agents SHOULD NOT close (e.g. a script using the WebSocket API), user agents SHOULD NOT close
the connection. the connection.
7.2. Abnormal closures 7.2. Abnormal closures
7.2.1. Client-initiated closure 7.2.1. Client-initiated closure
Certain algorithms, namely during the initial handshake, require the Certain algorithms, namely during the initial handshake, require the
user agent to *fail the WebSocket connection*. To do so, the user user agent to *fail the WebSocket connection*. To do so, the user
agent must _Close the WebSocket connection_ as previously defined, agent MUST _Close the WebSocket connection_ as previously defined,
and may report the problem to the user via an appropriate mechanism and MAY report the problem to the user via an appropriate mechanism
(which would be especially useful for developers). (which would be especially useful for developers).
Except as indicated above or as specified by the application layer Except as indicated above or as specified by the application layer
(e.g. a script using the WebSocket API), user agents should not close (e.g. a script using the WebSocket API), user agents SHOULD NOT close
the connection. the connection.
7.2.2. Server-initiated closure 7.2.2. Server-initiated closure
Certain algorithms require or recommend that the server _abort the Certain algorithms require or recommend that the server _abort the
WebSocket connection_ during the opening handshake. To do so, the WebSocket connection_ during the opening handshake. To do so, the
server must simply _close the WebSocket connection_ (Section 7.1.1). server MUST simply _close the WebSocket connection_ (Section 7.1.1).
7.3. Normal closure of connections 7.3. Normal closure of connections
Servers MAY close the WebSocket connection whenever desired. User Servers MAY close the WebSocket connection whenever desired. User
agents SHOULD NOT close the WebSocket connection arbitrarily. In agents SHOULD NOT close the WebSocket connection arbitrarily. In
either case, an endpoint initiates a closure by following the either case, an endpoint initiates a closure by following the
procedures to _start the WebSocket closing handshake_ procedures to _start the WebSocket closing handshake_
(Section 7.1.2). (Section 7.1.2).
7.4. Status codes 7.4. Status codes
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1002 1002
1002 indicates that an endpoint is terminating the connection due 1002 indicates that an endpoint is terminating the connection due
to a protocol error. to a protocol error.
1003 1003
1003 indicates that an endpoint is terminating the connection 1003 indicates that an endpoint is terminating the connection
because it has received a type of data it cannot accept (e.g. an because it has received a type of data it cannot accept (e.g. an
endpoint that understands only text data may send this if it endpoint that understands only text data MAY send this if it
receives a binary message.) receives a binary message).
1004 1004
1004 indicates that an endpoint is terminating the connection 1004 indicates that an endpoint is terminating the connection
because it has received a message that is too large. because it has received a message that is too large.
7.4.2. Reserved status code ranges 7.4.2. Reserved status code ranges
0-999 0-999
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3000-3999 3000-3999
Status codes in the range 3000-3999 MAY be used by libraries and Status codes in the range 3000-3999 MAY be used by libraries and
frameworks. The interpretation of these codes is undefined by frameworks. The interpretation of these codes is undefined by
this protocol. End applications MUST NOT use status codes in this this protocol. End applications MUST NOT use status codes in this
range. range.
4000-4999 4000-4999
Status codes in the range 4000-4999 MAY be used by application Status codes in the range 4000-4999 MAY be used by application
code. The interpretaion of these codes is undefined by this code. The interpretation of these codes is undefined by this
protocol. protocol.
8. Extensions 8. Extensions
WebSocket clients MAY request extensions to this specification, and WebSocket clients MAY request extensions to this specification, and
WebSocket servers MAY accept some or all extensions requested by the WebSocket servers MAY accept some or all extensions requested by the
client. A server MUST NOT respond with any extension not requested client. A server MUST NOT respond with any extension not requested
by the client. If extension parameters are included in negotiations by the client. If extension parameters are included in negotiations
between the client and the server, those parameters MUST be chosen in between the client and the server, those parameters MUST be chosen in
accordance with the specification of the extension to which the accordance with the specification of the extension to which the
parameters apply. parameters apply.
8.1. Negotiating extensions 8.1. Negotiating extensions
A client requests extensions by including a "Sec-WebSocket- A client requests extensions by including a "Sec-WebSocket-
Extensions" header, which follows the normal rules for HTTP headers Extensions" header, which follows the normal rules for HTTP headers
(see [RFC2616] section 4.2) and the value of the header is defined by (see [RFC2616] section 4.2) and the value of the header is defined by
the following ABNF: the following ABNF. Note that unlike other section of the document
this section is using ABNF syntax/rules from [RFC2616].
extension-list = 1#extension extension-list = 1#extension
extension = extension-token *( ";" extension-param ) extension = extension-token *( ";" extension-param )
extension-token = registered-token | private-use-token extension-token = registered-token | private-use-token
registered-token = token registered-token = token
private-use-token = "x-" token private-use-token = "x-" token
extension-param = token [ "=" ( token | quoted-string ) ] extension-param = token [ "=" ( token | quoted-string ) ]
Note that like other HTTP headers, this header may be split or Note that like other HTTP headers, this header MAY be split or
combined across multiple lines. Ergo, the following are equivalent: combined across multiple lines. Ergo, the following are equivalent:
Sec-WebSocket-Extensions: foo Sec-WebSocket-Extensions: foo
Sec-WebSocket-Extensions: bar; baz=2 Sec-WebSocket-Extensions: bar; baz=2
is exactly equivalent to is exactly equivalent to
Sec-WebSocket-Extensions: foo, bar; baz=2 Sec-WebSocket-Extensions: foo, bar; baz=2
Any extension-token used must either be a registered token Any extension-token used MUST either be a registered token
(registration TBD), or have a prefix of "x-" to indicate a private- (registration TBD), or have a prefix of "x-" to indicate a private-
use token. The parameters supplied with any given extension MUST be use token. The parameters supplied with any given extension MUST be
defined for that extension. Note that the client is only offering to defined for that extension. Note that the client is only offering to
use any advertised extensions, and MUST NOT use them unless the use any advertised extensions, and MUST NOT use them unless the
server accepts the extension. server indicates that it wishes to use the extension.
Note that the order of extensions is significant. Any interactions Note that the order of extensions is significant. Any interactions
between multiple extensions MAY be defined in the documents defining between multiple extensions MAY be defined in the documents defining
the extensions. In the absence of such definition, the the extensions. In the absence of such definition, the
interpretation is that the headers listed by the client in its interpretation is that the headers listed by the client in its
request represent a preference of the headers it wishes to use, with request represent a preference of the headers it wishes to use, with
the first options listed being most preferable. The extensions the first options listed being most preferable. The extensions
listed by the server in response represent the extensions actually in listed by the server in response represent the extensions actually in
use. Should the extensions modify the data and/or framing, the order use for the connection. Should the extensions modify the data and/or
of operations on the data should be assumed to be the same as the framing, the order of operations on the data should be assumed to be
order in which the extensions are listed in the server's response in the same as the order in which the extensions are listed in the
the opening handshake. server's response in the opening handshake.
For example, if there are two extensions "foo" and "bar", if the For example, if there are two extensions "foo" and "bar", if the
header |Sec-WebSocket-Extensions| sent by the server has the value header |Sec-WebSocket-Extensions| sent by the server has the value
"foo, bar" then operations on the data will be made as "foo, bar" then operations on the data will be made as
bar(foo(data)), be those changes to the data itself (such as bar(foo(data)), be those changes to the data itself (such as
compression) or changes to the framing thay may "stack". compression) or changes to the framing thay may "stack".
Non-normative examples of acceptable extension headers: Non-normative examples of acceptable extension headers:
Sec-WebSocket-Extensions: deflate-stream Sec-WebSocket-Extensions: deflate-stream
skipping to change at page 38, line 32 skipping to change at page 42, line 33
WebSocket-Extensions| header containing one or more extensions which WebSocket-Extensions| header containing one or more extensions which
were requested by the client. The interpretation of any extension were requested by the client. The interpretation of any extension
parameters, and what constitutes a valid response by a server to a parameters, and what constitutes a valid response by a server to a
requested set of parameters by a client, will be defined by each such requested set of parameters by a client, will be defined by each such
extension. extension.
8.2. Known extensions 8.2. Known extensions
Extensions provide a mechanism for implementations to opt-in to Extensions provide a mechanism for implementations to opt-in to
additional protocol features. This section defines the meaning of additional protocol features. This section defines the meaning of
well-known extensions but implementations may use extensions defined well-known extensions but implementations MAY use extensions defined
separately as well. separately as well.
8.2.1. Compression 8.2.1. Compression
The registered extension token for this compression extension is The registered extension token for this compression extension is
"deflate-stream". "deflate-stream".
The extension does not have any per message extension data and it The extension does not have any per message extension data and it
does not define the use of any WebSocket reserved bits or op codes. does not define the use of any WebSocket reserved bits or op codes.
Senders using this extension MUST apply RFC 1951 encodings to all Senders using this extension MUST apply RFC 1951 encodings to all
bytes of the data stream following the handshake including both data bytes of the data stream following the handshake including both data
and control messages. The data stream MAY include multiple blocks of and control messages. The data stream MAY include multiple blocks of
both compressed and uncompressed types as defined by RFC 1951. both compressed and uncompressed types as defined by [RFC1951].
[RFC1951]
Senders MUST NOT delay the transmission of any portion of a WebSocket Senders MUST NOT delay the transmission of any portion of a WebSocket
message because the deflate encoding of the message does not end on a message because the deflate encoding of the message does not end on a
byte boundary. The encodings for adjacent messages MAY appear in the byte boundary. The encodings for adjacent messages MAY appear in the
same byte if no delay in transmission is occurred by doing so. same byte if no delay in transmission is occurred by doing so.
Historically there have been some confusion and interoperability
problems around the specification of compression algorithms. In this
specification "deflate-stream" requires a [RFC1951] deflate encoding.
It MUST NOT be wrapped in any of the header formats often associated
with RFC 1951 such as "zlib" [RFC1950]. This requirement is given
special attention with this note because of confusion in this area,
the presence of some popular open source libraries that create both
formats under a single API call with confusing naming conventions,
and the fact that the popular HTTP [RFC2616] specification defines
"deflate" compression differently than this specification.
9. Security considerations 9. Security considerations
While this protocol is intended to be used by scripts in Web pages, While this protocol is intended to be used by scripts in Web pages,
it can also be used directly by hosts. Such hosts are acting on it can also be used directly by hosts. Such hosts are acting on
their own behalf, and can therefore send fake "Origin" fields, their own behalf, and can therefore send fake "Origin" fields,
misleading the server. Servers should therefore be careful about misleading the server. Servers should therefore be careful about
assuming that they are talking directly to scripts from known assuming that they are talking directly to scripts from known
origins, and must consider that they might be accessed in unexpected origins, and must consider that they might be accessed in unexpected
ways. In particular, a server should not trust that any input is ways. In particular, a server should not trust that any input is
valid. valid.
EXAMPLE: For example, if the server uses input as part of SQL EXAMPLE: For example, if the server uses input as part of SQL
queries, all input text should be escaped before being passed to the queries, all input text should be escaped before being passed to the
SQL server, lest the server be susceptible to SQL injection. SQL server, lest the server be susceptible to SQL injection.
Servers that are not intended to process input from any Web page but Servers that are not intended to process input from any Web page but
only for certain sites should verify the "Origin" field is an origin only for certain sites SHOULD verify the "Origin" field is an origin
they expect, and should only respond with the corresponding "Sec- they expect, and should only respond with the corresponding "Sec-
WebSocket-Origin" if it is an accepted origin. Servers that only WebSocket-Origin" if it is an accepted origin. Servers that only
accept input from one origin can just send back that value in the accept input from one origin can just send back that value in the
"Sec-WebSocket-Origin" field, without bothering to check the client's "Sec-WebSocket-Origin" field, without bothering to check the client's
value. value.
If at any time a server is faced with data that it does not If at any time a server is faced with data that it does not
understand, or that violates some criteria by which the server understand, or that violates some criteria by which the server
determines safety of input, or when the server sees a handshake that determines safety of input, or when the server sees a handshake that
does not correspond to the values the server is expecting (e.g. does not correspond to the values the server is expecting (e.g.
incorrect path or origin), the server should just disconnect. It is incorrect path or origin), the server SHOULD just disconnect. It is
always safe to disconnect. always safe to disconnect.
The biggest security risk when sending text data using this protocol The biggest security risk when sending text data using this protocol
is sending data using the wrong encoding. If an attacker can trick is sending data using the wrong encoding. If an attacker can trick
the server into sending data encoded as ISO-8859-1 verbatim (for the server into sending data encoded as ISO-8859-1 verbatim (for
instance), rather than encoded as UTF-8, then the attacker could instance), rather than encoded as UTF-8, then the attacker could
inject arbitrary frames into the data stream. inject arbitrary frames into the data stream.
In addition to endpoints being the target of attacks via WebSockets, In addition to endpoints being the target of attacks via WebSockets,
other parts of web infrastructure, such as proxies, may be the other parts of web infrastructure, such as proxies, may be the
skipping to change at page 42, line 5 skipping to change at page 45, line 12
browser to send a message that looks to an intermediary like a GET browser to send a message that looks to an intermediary like a GET
request for a common piece of JavaScript on another domain, and send request for a common piece of JavaScript on another domain, and send
back a message that is interpreted as a cacheable response to that back a message that is interpreted as a cacheable response to that
request, thus poisioning the cache for other users. To prevent this request, thus poisioning the cache for other users. To prevent this
attack, messages sent from clients are masked on the wire with a 32- attack, messages sent from clients are masked on the wire with a 32-
bit value, to prevent an attacker from controlling the bits on the bit value, to prevent an attacker from controlling the bits on the
wire and thus lessen the probability of an attacker being able to wire and thus lessen the probability of an attacker being able to
construct a message that can be misinterpreted by a proxy as a non- construct a message that can be misinterpreted by a proxy as a non-
WebSocket request. WebSocket request.
As mentioned in Section 6.2, servers must be extremely cautious
interpreting invalid UTF-8 data from the client. A naive UTF-8
parsing implementation can result in buffer overflows in the case of
invalid input data.
10. IANA considerations 10. IANA considerations
10.1. Registration of ws: scheme 10.1. Registration of ws: scheme
A |ws:| URI identifies a WebSocket server and resource name. A |ws:| URI identifies a WebSocket server and resource name.
URI scheme name. URI scheme name.
ws ws
Status. Status.
Permanent. Permanent.
URI scheme syntax. URI scheme syntax.
In ABNF terms using the terminals from the URI specifications: In ABNF terms using the terminals from the URI specifications:
[RFC5234] [RFC3986] [RFC5234] [RFC3986]
"ws" ":" hier-part [ "?" query ] "ws" ":" hier-part [ "?" query ]
The path and query components form the resource name sent to the The <path> [RFC3986] and <query> components form the resource name
server to identify the kind of service desired. Other components sent to the server to identify the kind of service desired. Other
have the meanings described in RFC3986. components have the meanings described in RFC3986.
URI scheme semantics. URI scheme semantics.
The only operation for this scheme is to open a connection using The only operation for this scheme is to open a connection using
the WebSocket protocol. the WebSocket protocol.
Encoding considerations. Encoding considerations.
Characters in the host component that are excluded by the syntax Characters in the host component that are excluded by the syntax
defined above must be converted from Unicode to ASCII by applying defined above MUST be converted from Unicode to ASCII by applying
the IDNA ToASCII algorithm to the Unicode host name, with both the the IDNA ToASCII algorithm to the Unicode host name, with both the
AllowUnassigned and UseSTD3ASCIIRules flags set, and using the AllowUnassigned and UseSTD3ASCIIRules flags set, and using the
result of this algorithm as the host in the URI. [RFC3490] result of this algorithm as the host in the URI. [RFC3490]
Characters in other components that are excluded by the syntax Characters in other components that are excluded by the syntax
defined above must be converted from Unicode to ASCII by first defined above MUST be converted from Unicode to ASCII by first
encoding the characters as UTF-8 and then replacing the encoding the characters as UTF-8 and then replacing the
corresponding bytes using their percent-encoded form as defined in corresponding bytes using their percent-encoded form as defined in
the URI and IRI specification. [RFC3986] [RFC3987] the URI and IRI specifications. [RFC3986] [RFC3987]
Applications/protocols that use this URI scheme name. Applications/protocols that use this URI scheme name.
WebSocket protocol. WebSocket protocol.
Interoperability considerations. Interoperability considerations.
None. None.
Security considerations. Security considerations.
See "Security considerations" section above. See "Security considerations" section above.
Contact. Contact.
Ian Hickson <ian@hixie.ch> HYBI WG <hybi@ietf.org>
Author/Change controller. Author/Change controller.
Ian Hickson <ian@hixie.ch> IETF <iesg@ietf.org>
References. References.
This document. RFC XXXX
10.2. Registration of wss: scheme 10.2. Registration of wss: scheme
A |wss:| URI identifies a WebSocket server and resource name, and A |wss:| URI identifies a WebSocket server and resource name, and
indicates that traffic over that connection is to be encrypted. indicates that traffic over that connection is to be encrypted.
URI scheme name. URI scheme name.
wss wss
Status. Status.
Permanent. Permanent.
URI scheme syntax. URI scheme syntax.
In ABNF terms using the terminals from the URI specifications: In ABNF terms using the terminals from the URI specifications:
[RFC5234] [RFC3986] [RFC5234] [RFC3986]
"wss" ":" hier-part [ "?" query ] "wss" ":" hier-part [ "?" query ]
The path and query components form the resource name sent to the The <path> and <query> components form the resource name sent to
server to identify the kind of service desired. Other components the server to identify the kind of service desired. Other
have the meanings described in RFC3986. components have the meanings described in RFC3986.
URI scheme semantics. URI scheme semantics.
The only operation for this scheme is to open a connection using The only operation for this scheme is to open a connection using
the WebSocket protocol, encrypted using TLS. the WebSocket protocol, encrypted using TLS.
Encoding considerations. Encoding considerations.
Characters in the host component that are excluded by the syntax Characters in the host component that are excluded by the syntax
defined above must be converted from Unicode to ASCII by applying defined above MUST be converted from Unicode to ASCII by applying
the IDNA ToASCII algorithm to the Unicode host name, with both the the IDNA ToASCII algorithm to the Unicode host name, with both the
AllowUnassigned and UseSTD3ASCIIRules flags set, and using the AllowUnassigned and UseSTD3ASCIIRules flags set, and using the
result of this algorithm as the host in the URI. [RFC3490] result of this algorithm as the host in the URI. [RFC3490]
Characters in other components that are excluded by the syntax Characters in other components that are excluded by the syntax
defined above must be converted from Unicode to ASCII by first defined above MUST be converted from Unicode to ASCII by first
encoding the characters as UTF-8 and then replacing the encoding the characters as UTF-8 and then replacing the
corresponding bytes using their percent-encoded form as defined in corresponding bytes using their percent-encoded form as defined in
the URI and IRI specification. [RFC3986] [RFC3987] the URI and IRI specification. [RFC3986] [RFC3987]
Applications/protocols that use this URI scheme name. Applications/protocols that use this URI scheme name.
WebSocket protocol over TLS. WebSocket protocol over TLS.
Interoperability considerations. Interoperability considerations.
None. None.
Security considerations. Security considerations.
See "Security considerations" section above. See "Security considerations" section above.
Contact. Contact.
Ian Hickson <ian@hixie.ch> HYBI WG <hybi@ietf.org>
Author/Change controller. Author/Change controller.
Ian Hickson <ian@hixie.ch> IETF <iesg@ietf.org>
References. References.
This document. RFC XXXX
10.3. Registration of the "WebSocket" HTTP Upgrade keyword 10.3. Registration of the "WebSocket" HTTP Upgrade keyword
Name of token. Name of token.
WebSocket WebSocket
Author/Change controller. Author/Change controller.
Ian Hickson <ian@hixie.ch> IETF <iesg@ietf.org>
Contact. Contact.
Ian Hickson <ian@hixie.ch> HYBI <hybi@ietf.org>
References. References.
This document. RFC XXXX
10.4. Sec-WebSocket-Key 10.4. Sec-WebSocket-Key
This section describes a header field for registration in the This section describes a header field for registration in the
Permanent Message Header Field Registry. [RFC3864] Permanent Message Header Field Registry. [RFC3864]
Header field name Header field name
Sec-WebSocket-Key Sec-WebSocket-Key
Applicable protocol Applicable protocol
http http
Status Status
reserved; do not use outside WebSocket handshake standard
Author/Change controller Author/Change controller
IETF IETF
Specification document(s) Specification document(s)
This document is the relevant specification. RFC XXXX
Related information Related information
None. This header field is only used for WebSocket handshake.
The |Sec-WebSocket-Key| header is used in the WebSocket handshake. The |Sec-WebSocket-Key| header is used in the WebSocket handshake.
It is sent from the client to the server to provide part of the It is sent from the client to the server to provide part of the
information used by the server to prove that it received a valid information used by the server to prove that it received a valid
WebSocket handshake. This helps ensure that the server does not WebSocket handshake. This helps ensure that the server does not
accept connections from non-WebSocket clients (e.g. HTTP clients) accept connections from non-WebSocket clients (e.g. HTTP clients)
that are being abused to send data to unsuspecting WebSocket servers. that are being abused to send data to unsuspecting WebSocket servers.
10.5. Sec-WebSocket-Extensions 10.5. Sec-WebSocket-Extensions
This section describes a header field for registration in the This section describes a header field for registration in the
Permanent Message Header Field Registry. [RFC3864] Permanent Message Header Field Registry. [RFC3864]
Header field name Header field name
Sec-WebSocket-Extensions Sec-WebSocket-Extensions
Applicable protocol Applicable protocol
http http
Status Status
reserved; do not use outside WebSocket handshake standard
Author/Change controller Author/Change controller
IETF IETF
Specification document(s) Specification document(s)
This document is the relevant specification. RFC XXXX
Related information Related information
None. This header field is only used for WebSocket handshake.
The |Sec-WebSocket-Extensions| header is used in the WebSocket The |Sec-WebSocket-Extensions| header is used in the WebSocket
handshake. It is initially sent from the client to the server, and handshake. It is initially sent from the client to the server, and
then subsequently sent from the servver to the client, to agree on a then subsequently sent from the server to the client, to agree on a
set of protocol-level extensions to use during the connection. set of protocol-level extensions to use for the duration of the
connection.
10.6. Sec-WebSocket-Accept 10.6. Sec-WebSocket-Accept
This section describes a header field for registration in the This section describes a header field for registration in the
Permanent Message Header Field Registry. [RFC3864] Permanent Message Header Field Registry. [RFC3864]
Header field name Header field name
Sec-WebSocket-Accept Sec-WebSocket-Accept
Applicable protocol Applicable protocol
http http
Status Status
reserved; do not use outside WebSocket handshake standard
Author/Change controller Author/Change controller
IETF IETF
Specification document(s) Specification document(s)
This document is the relevant specification. RFC XXXX
Related information Related information
None. This header field is only used for WebSocket handshake.
The |Sec-WebSocket-Accept| header is used in the WebSocket handshake. The |Sec-WebSocket-Accept| header is used in the WebSocket handshake.
It is sent from the server to the client to confirm that the server It is sent from the server to the client to confirm that the server
is willing to initiate the connection. is willing to initiate the connection.
10.7. Sec-WebSocket-Origin 10.7. Sec-WebSocket-Origin
This section describes a header field for registration in the This section describes a header field for registration in the
Permanent Message Header Field Registry. [RFC3864] Permanent Message Header Field Registry. [RFC3864]
Header field name Header field name
Sec-WebSocket-Origin Sec-WebSocket-Origin
Applicable protocol Applicable protocol
http http
Status Status
reserved; do not use outside WebSocket handshake standard
Author/Change controller Author/Change controller
IETF IETF
Specification document(s) Specification document(s)
This document is the relevant specification. RFC XXXX
Related information Related information
None. This header field is only used for WebSocket handshake.
The |Sec-WebSocket-Origin| header is used in the WebSocket handshake. The |Sec-WebSocket-Origin| header is used in the WebSocket handshake.
It is sent from the server to the client to confirm the origin of the It is sent from the server to the client to confirm the origin of the
script that opened the connection. This enables user agents to script that opened the connection. This enables user agents to
verify that the server is willing to serve the script that opened the verify that the server is willing to serve the script that opened the
connection. connection.
10.8. Sec-WebSocket-Protocol 10.8. Sec-WebSocket-Protocol
This section describes a header field for registration in the This section describes a header field for registration in the
Permanent Message Header Field Registry. [RFC3864] Permanent Message Header Field Registry. [RFC3864]
Header field name Header field name
Sec-WebSocket-Protocol Sec-WebSocket-Protocol
Applicable protocol Applicable protocol
http http
Status Status
reserved; do not use outside WebSocket handshake standard
Author/Change controller Author/Change controller
IETF IETF
Specification document(s) Specification document(s)
This document is the relevant specification. RFC XXXX
Related information Related information
None. This header field is only used for WebSocket handshake.
The |Sec-WebSocket-Protocol| header is used in the WebSocket The |Sec-WebSocket-Protocol| header is used in the WebSocket
handshake. It is sent from the client to the server and back from handshake. It is sent from the client to the server and back from
the server to the client to confirm the subprotocol of the the server to the client to confirm the subprotocol of the
connection. This enables scripts to both select a subprotocol and be connection. This enables scripts to both select a subprotocol and be
sure that the server agreed to serve that subprotocol. sure that the server agreed to serve that subprotocol.
10.9. Sec-WebSocket-Version 10.9. Sec-WebSocket-Version
This section describes a header field for registration in the This section describes a header field for registration in the
Permanent Message Header Field Registry. [RFC3864] Permanent Message Header Field Registry. [RFC3864]
Header field name Header field name
Sec-WebSocket-Version Sec-WebSocket-Version
Applicable protocol Applicable protocol
http http
Status Status
reserved; do not use outside WebSocket handshake standard
Author/Change controller Author/Change controller
IETF IETF
Specification document(s) Specification document(s)
This document is the relevant specification. RFC XXXX
Related information Related information
None. This header field is only used for WebSocket handshake.
The |Sec-WebSocket-Version| header is used in the WebSocket The |Sec-WebSocket-Version| header is used in the WebSocket
handshake. It is sent from the client to the server to indicate the handshake. It is sent from the client to the server to indicate the
protocol version of the connection. This enables servers to protocol version of the connection. This enables servers to
correctly interpret the handshake and subsequent data being sent from correctly interpret the handshake and subsequent data being sent from
the data, and close the connection if the server cannot interpret the data, and close the connection if the server cannot interpret
that data in a safe manner. that data in a safe manner.
11. Using the WebSocket protocol from other specifications 11. Using the WebSocket protocol from other specifications
skipping to change at page 51, line 5 skipping to change at page 55, line 5
specification is given in the WHATWG HTML specification at specification is given in the WHATWG HTML specification at
http://whatwg.org/html5. http://whatwg.org/html5.
Special thanks also to John Tamplin for providing a significant Special thanks also to John Tamplin for providing a significant
amount of text for the Data Framing section of this specification. amount of text for the Data Framing section of this specification.
Special thanks also to Adam Barth for providing a significant amount Special thanks also to Adam Barth for providing a significant amount
of text and background research for the Data Masking section of this of text and background research for the Data Masking section of this
specification. specification.
13. Appendix: List of Changes 13. References
This section is not normative. This section was added at the request
of the chairs to help track changes between versions. This section
will be removed from the final version of this document.
13.1. Changes from -05 to -06
Two major areas were changed in this draft. The closing handshake
was clarified and re-written to add in terminology matching the API
specification. The close frame was given an optional status code to
indicate closure reason, and the notion of a body indicating which
side initiated the close removed. Aside from this, many areas were
clarified in areas previously ambiguous, though the meaning should
remain consistent with the intent of previous drafts. Certain other
material changes that are not as large as those previously mentioned
are listed below, though for a complete list readers are reminded
that a tool is available to diff two versions at
http://tools.ietf.org/tools/rfcdiff/. The list below is my attempt
at a changelog, not an authoritative guarantee, plese use the diff
tool for a complete list.
o Clarified that Sec-WebSocket-Origin is optional for non-browser
clients.
o Clarified the semantics of the closing handshake to be that the
connection is closed when an endpoint has both sent and received a
close frame.
o Changed text around final HTTP responses and the WebSocket
handshake.
o Removed Sec-WebSocket-Nonce
o Attempted to convert use of URL to URI terminology. (Ticket 41)
o Attempted to resolve Ticket 42 re: HTML spec reference.
o Edited potentially misleadin text around the word "even" in
Section 1.6 and what applied to XHR vs more broadly.
o Removed non-material text from 1.8 about establishing a
connection.
o Clarified text in the section about fragmentation (4.4). No
material changes, clarification only.
o Clarified that control frames (4.5) may be interjected in the
middle of a fragmented message.
o Clarified what was meant by the body of a close frame.
o Clarified the intent in 5.1 that there be only one connection in
CONNECTING state.
o Cleaned 1.5 up to note that compression was already introduced in
the spec, left in multiplexing as a future definition.
o Randomly selected randomly - typo fix.
o Added a change log in the appendix.
o Included in security considerations a description of the attack
presented by Adam Barth.
o Changed some referneces from Web-Socket to WebSocket
o Clarified in 3.1 that only ws and wss are valid options, and that
other schemes should result in a failure.
o Various cleanups around terminology of "host", "endpoint", and
"user agent".
o Defined status codes and reserved ranges for close frames.
o Added text that a TCP connection should be shut down cleanly.
o Clarified whether the upgrade header exactly equaled upgrade or
contained an upgrade token.
14. Normative References 13.1. Normative References
[ANSI.X3-4.1986] [ANSI.X3-4.1986]
American National Standards Institute, "Coded Character American National Standards Institute, "Coded Character
Set - 7-bit American Standard Code for Information Set - 7-bit American Standard Code for Information
Interchange", ANSI X3.4, 1986. Interchange", ANSI X3.4, 1986.
[FIPS.180-2.2002] [FIPS.180-2.2002]
National Institute of Standards and Technology, "Secure National Institute of Standards and Technology, "Secure
Hash Standard", FIPS PUB 180-2, August 2002, <http:// Hash Standard", FIPS PUB 180-2, August 2002, <http://
csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf>. csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf>.
[RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification
version 1.3", RFC 1951, May 1996. version 1.3", RFC 1951, May 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)", "Internationalizing Domain Names in Applications (IDNA)",
RFC 3490, March 2003. RFC 3490, March 2003.
[RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode
for Internationalized Domain Names in Applications
(IDNA)", RFC 3492, March 2003.
[RFC3548] Josefsson, S., "The Base16, Base32, and Base64 Data [RFC3548] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 3548, July 2003. Encodings", RFC 3548, July 2003.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003. 10646", STD 63, RFC 3629, November 2003.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration [RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864, Procedures for Message Header Fields", BCP 90, RFC 3864,
September 2004. September 2004.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005. RFC 3986, January 2005.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005. Identifiers (IRIs)", RFC 3987, January 2005.
[RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
and T. Wright, "Transport Layer Security (TLS) (TLS) Protocol Version 1.2", RFC 5246, August 2008.
Extensions", RFC 4366, April 2006.
[RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions:
Extension Definitions", RFC 6066, January 2011.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
13.2. Informative References
[WSAPI] Hickson, I., "The Web Sockets API", August 2010,
<http://dev.w3.org/html5/websockets/>.
[I-D.ietf-httpstate-cookie] [I-D.ietf-httpstate-cookie]
Barth, A., "HTTP State Management Mechanism", Barth, A., "HTTP State Management Mechanism",
draft-ietf-httpstate-cookie-20 (work in progress), draft-ietf-httpstate-cookie-20 (work in progress),
December 2010. December 2010.
[I-D.ietf-websec-origin] [I-D.ietf-websec-origin]
Barth, A., "The Web Origin Concept", Barth, A., "The Web Origin Concept",
draft-ietf-websec-origin-00 (work in progress), draft-ietf-websec-origin-00 (work in progress),
December 2010. December 2010.
[WSAPI] Hickson, I., "The Web Sockets API", August 2010, [RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data Format
<http://dev.w3.org/html5/websockets/>. Specification version 3.3", RFC 1950, May 1996.
[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
October 2008.
[RFC6202] Loreto, S., Saint-Andre, P., Salsano, S., and G. Wilkins,
"Known Issues and Best Practices for the Use of Long
Polling and Streaming in Bidirectional HTTP", RFC 6202,
April 2011.
Author's Address Author's Address
Ian Fette Ian Fette
Google, Inc. Google, Inc.
Email: ifette+ietf@google.com Email: ifette+ietf@google.com
URI: http://www.ianfette.com/ URI: http://www.ianfette.com/
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