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Network Working Group I. Hickson
Internet-Draft Google, Inc.
Intended status: Standards Track February 25, 2009
Expires: August 29, 2009
The Web Socket protocol
draft-hixie-thewebsocketprotocol-03
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 29, 2009.
Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Abstract
This protocol enables two-way communication between a user agent
running untrusted code running in a controlled environment to a
remote host that understands the protocol. It is intended to fail to
communicate with servers of pre-existing protocols like SMTP or HTTP,
while allowing HTTP servers to opt-in to supporting this protocol if
desired. It is designed to be easy to implement on the server side.
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Author's note
This document is automatically generated from, and is therefore a
subset of, the HTML5 specification produced by the WHATWG. [HTML5]
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Client-side requirements . . . . . . . . . . . . . . . . . . . 5
2.1. Handshake . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Data framing . . . . . . . . . . . . . . . . . . . . . . . 11
3. Server-side requirements . . . . . . . . . . . . . . . . . . . 13
3.1. Minimal handshake . . . . . . . . . . . . . . . . . . . . 13
3.2. Handshake details . . . . . . . . . . . . . . . . . . . . 13
3.3. Data framing . . . . . . . . . . . . . . . . . . . . . . . 14
4. Closing the connection . . . . . . . . . . . . . . . . . . . . 16
5. Security considerations . . . . . . . . . . . . . . . . . . . 17
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 18
7. Normative References . . . . . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 20
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1. Introduction
** ISSUE ** ...
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2. Client-side requirements
_This section only applies to user agents, not to servers._
NOTE: This specification doesn't currently define a limit to the
number of simultaneous connections that a client can establish to a
server.
2.1. Handshake
When the user agent is to *establish a Web Socket connection* to a
host /host/, optionally on port /port/, from an origin /origin/, with
a flag /secure/, and with a particular /resource name/, it must run
the following steps.
NOTE: The /host/ and /origin/ strings will be all-lowercase when this
algorithm is invoked.
1. If there is no explicit /port/, then: if /secure/ is false, let
/port/ be 81, otherwise let /port/ be 815.
2. If the user agent is configured to use a proxy to connect to
host /host/ and/or port /port/, then connect to that proxy and
ask it to open a TCP/IP connection to the host given by /host/
and the port given by /port/.
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 server example.com, it might send the following lines to
the proxy server:
CONNECT example.com HTTP/1.1
If there was a password, the connection might look like:
CONNECT example.com HTTP/1.1
Proxy-authorization: Basic ZWRuYW1vZGU6bm9jYXBlcyE=
Otherwise, if the user agent is not configured to use a proxy,
then open a TCP/IP connection to the host given by /host/ and
the port given by /port/.
3. If the connection could not be opened, then fail the Web Socket
connection and abort these steps.
4. If /secure/ is true, perform a TLS handshake over the
connection. If this fails (e.g. the server's certificate could
not be verified), then fail the Web Socket connection and abort
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these steps. Otherwise, all further communication on this
channel must run through the encrypted tunnel. [RFC2246]
5. Send the following bytes to the remote side (the server):
47 45 54 20
Send the /resource name/ value, encoded as US-ASCII.
Send the following bytes:
20 48 54 54 50 2f 31 2e 31 0d 0a 55 70 67 72 61
64 65 3a 20 57 65 62 53 6f 63 6b 65 74 0d 0a 43
6f 6e 6e 65 63 74 69 6f 6e 3a 20 55 70 67 72 61
64 65 0d 0a
NOTE: The string "GET ", the path, " HTTP/1.1", CRLF, the string
"Upgrade: WebSocket", CRLF, and the string "Connection:
Upgrade", CRLF.
6. Send the following bytes:
48 6f 73 74 3a 20
Send the /host/ value, encoded as US-ASCII.
Send the following bytes:
0d 0a
NOTE: The string "Host: ", the host, and CRLF.
7. Send the following bytes:
4f 72 69 67 69 6e 3a 20
Send the /origin/ value, encoded as US-ASCII.
NOTE: The /origin/ value is a string that was passed to this
algorithm.
Send the following bytes:
0d 0a
NOTE: The string "Origin: ", the origin, and CRLF.
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8. If the client has any authentication information or cookies that
would be relevant to a resource accessed over HTTP, if /secure/
is false, or HTTPS, if it is true, on host /host/, port /port/,
with /resource name/ as the path (and possibly query
parameters), then HTTP headers that would be appropriate for
that information should be sent at this point. [RFC2616]
[RFC2109] [RFC2965]
Each header must be on a line of its own (each ending with a CR
LF sequence). For the purposes of this step, each header must
not be split into multiple lines (despite HTTP otherwise
allowing this with continuation lines).
EXAMPLE: For example, if the server had a username and
password that applied to |http://example.com/socket|, and the
Web Socket was being opened to |ws://example.com:80/socket|,
it could send them:
Authorization: Basic d2FsbGU6ZXZl
However, it would not send them if the Web Socket was being
opened to |ws://example.com/socket|, as that uses a different
port (81, not 80).
9. Send the following bytes:
0d 0a
NOTE: Just a CRLF (a blank line).
10. Read the first 85 bytes from the server. If the connection
closes before 85 bytes are received, or if the first 85 bytes
aren't exactly equal to the following bytes, then fail the Web
Socket connection and abort these steps.
48 54 54 50 2f 31 2e 31 20 31 30 31 20 57 65 62
20 53 6f 63 6b 65 74 20 50 72 6f 74 6f 63 6f 6c
20 48 61 6e 64 73 68 61 6b 65 0d 0a 55 70 67 72
61 64 65 3a 20 57 65 62 53 6f 63 6b 65 74 0d 0a
43 6f 6e 6e 65 63 74 69 6f 6e 3a 20 55 70 67 72
61 64 65 0d 0a
NOTE: The string "HTTP/1.1 101 Web Socket Protocol Handshake",
CRLF, the string "Upgrade: WebSocket", CRLF, the string
"Connection: Upgrade", CRLF.
11. Let /headers/ be a list of name-value pairs, initially empty.
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12. _Header_: Let /name/ and /value/ be empty byte arrays.
13. Read a byte from the server.
If the connection closes before this byte is received, then fail
the Web Socket connection and abort these steps.
Otherwise, handle the byte as described in the appropriate entry
below:
-> If the byte is 0x0d (ASCII CR)
If the /name/ byte array is empty, then jump to the headers
processing step. Otherwise, fail the Web Socket connection
and abort these steps.
-> If the byte is 0x0a (ASCII LF)
Fail the Web Socket connection and abort these steps.
-> If the byte is 0x3a (ASCII ":")
Move on to the next step.
-> If the byte is in the range 0x41 .. 0x5a (ASCII "A" .. "Z")
Append a byte whose value is the byte's value plus 0x20 to
the /name/ byte array and redo this step for the next byte.
-> Otherwise
Append the byte to the /name/ byte array and redo this step
for the next byte.
NOTE: This reads a header name, terminated by a colon,
converting upper-case ASCII letters to lowercase, and aborting
if a stray CR or LF is found.
14. Read a byte from the server.
If the connection closes before this byte is received, then fail
the Web Socket connection and abort these steps.
Otherwise, handle the byte as described in the appropriate entry
below:
-> If the byte is 0x20 (ASCII space)
Ignore the byte and move on to the next step.
-> Otherwise
Treat the byte as described by the list in the next step,
then move on to that next step for real.
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NOTE: This skips past a space character after the colon, if
necessary.
15. Read a byte from the server.
If the connection closes before this byte is received, then fail
the Web Socket connection and abort these steps.
Otherwise, handle the byte as described in the appropriate entry
below:
-> If the byte is 0x0d (ASCII CR)
Move on to the next step.
-> If the byte is 0x0a (ASCII LF)
Fail the Web Socket connection and abort these steps.
-> Otherwise
Append the byte to the /name/ byte array and redo this step
for the next byte.
NOTE: This reads a header value, terminated by a CRLF.
16. Read a byte from the server.
If the connection closes before this byte is received, or if the
byte is not a 0x0a byte (ASCII LF), then fail the Web Socket
connection and abort these steps.
NOTE: This skips past the LF byte of the CRLF after the header.
17. Append an entry to the /headers/ list that has the name given by
the string obtained by interpreting the /name/ byte array as a
UTF-8 byte stream and the value given by the string obtained by
interpreting the /value/ byte array as a UTF-8 byte stream.
18. Return to the header step above.
19. _Headers processing_: If there is not exactly one entry in the
/headers/ list whose name is "websocket-origin", or if there is
not exactly one entry in the /headers/ list whose name is
"websocket-location", or if there are any entries in the
/headers/ list whose names are the empty string, then fail the
Web Socket connection and abort these steps.
20. Handle each entry in the /headers/ list as follows:
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-> If the entry's name is "websocket-origin|"
If the value is not exactly equal to /origin/, converted to
lowercase, then fail the Web Socket connection and abort
these steps.
-> If the entry's name is "websocket-location|"
If the value is not exactly equal to a string consisting of
the following components in the same order, then fail the Web
Socket connection and abort these steps:
1. The string "ws" if /secure/ is false and "wss" if
/secure/ is true
2. The three characters "://".
3. The value of /host/.
4. If /secure/ is false and /port/ is not 81, or if /secure/
is true and /port/ is not 815: a ":" character followed
by the value of /port/.
5. The value of /resource name/.
-> If the entry's name is "set-cookie|" or "set-cookie2|" or
another cookie-related header name
Handle the cookie as defined by the appropriate spec, with
the resource being the one with the host /host/, the port
/port/, the path (and possibly query parameters) /resource
name/, and the scheme |http| if /secure/ is false and |https|
if /secure/ is true. [RFC2109] [RFC2965]
-> Any other name
Ignore it.
21. The *Web Socket connection is established*. Now the user agent
must send and receive to and from the connection as described in
the next section.
To *fail the Web Socket connection*, the user agent must close the
Web Socket connection, and may report the problem to the user (which
would be especially useful for developers). However, user agents
must not convey the failure information to the script that attempted
the connection in a way distinguishable from the Web Socket being
closed normally.
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2.2. Data framing
Once a Web Socket connection is established, the user agent must run
through the following state machine for the bytes sent by the server.
1. Try to read a byte from the server. Let /frame type/ be that
byte.
If no byte could be read because the Web Socket connection is
closed, then abort.
2. Handle the /frame type/ byte as follows:
If the high-order bit of the /frame type/ byte is set (i.e. if
/frame type/ _and_ed with 0x80 returns 0x80)
Run these steps. If at any point during these steps a read is
attempted but fails because the Web Socket connection is
closed, then abort.
1. Let /length/ be zero.
2. _Length_: Read a byte, let /b/ be that byte.
3. Let /b_v/ be integer corresponding to the low 7 bits of
/b/ (the value you would get by _and_ing /b/ with 0x7f).
4. Multiply /length/ by 128, add /b_v/ to that result, and
store the final result in /length/.
5. If the high-order bit of /b/ is set (i.e. if /b/ _and_ed
with 0x80 returns 0x80), then return to the step above
labeled _length_.
6. Read /length/ bytes.
7. Discard the read bytes.
If the high-order bit of the /frame type/ byte is _not_ set (i.e.
if /frame type/ _and_ed with 0x80 returns 0x00)
Run these steps. If at any point during these steps a read is
attempted but fails because the Web Socket connection is
closed, then abort.
1. Let /raw data/ be an empty byte array.
2. _Data_: Read a byte, let /b/ be that byte.
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3. If /b/ is not 0xff, then append /b/ to /raw data/ and
return to the previous step (labeled _data_).
4. Interpret /raw data/ as a UTF-8 string, and store that
string in /data/.
5. If /frame type/ is 0x00, then *a message has been
received* with text /data/. Otherwise, discard the data.
3. Return to the first step to read the next byte.
If the user agent is faced with content that is too large to be
handled appropriately, then it must fail the Web Socket connection.
Once a Web Socket connection is established, the user agent must use
the following steps to *send /data/ using the Web Socket*:
1. Send a 0x00 byte to the server.
2. Encode /data/ using UTF-8 and send the resulting byte stream to
the server.
3. Send a 0xff byte to the server.
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3. Server-side requirements
_This section only applies to servers._
3.1. Minimal handshake
NOTE: This section describes the minimal requirements for a server-
side implementation of Web Sockets.
Listen on a port for TCP/IP. Upon receiving a connection request,
open a connection and send the following bytes back to the client:
48 54 54 50 2f 31 2e 31 20 31 30 31 20 57 65 62
20 53 6f 63 6b 65 74 20 50 72 6f 74 6f 63 6f 6c
20 48 61 6e 64 73 68 61 6b 65 0d 0a 55 70 67 72
61 64 65 3a 20 57 65 62 53 6f 63 6b 65 74 0d 0a
43 6f 6e 6e 65 63 74 69 6f 6e 3a 20 55 70 67 72
61 64 65 0d 0a
Send the string "WebSocket-Origin" followed by a U+003A COLON (":")
followed by the ASCII serialization of the origin from which the
server is willing to accept connections, followed by a CRLF pair
(0x0d 0x0a).
For instance:
WebSocket-Origin: http://example.com
Send the string "WebSocket-Location" followed by a U+003A COLON (":")
followed by the URL of the Web Socket script, followed by a CRLF pair
(0x0d 0x0a).
For instance:
WebSocket-Location: ws://example.com:80/demo
Send another CRLF pair (0x0d 0x0a).
Read (and discard) data from the client until four bytes 0x0d 0x0a
0x0d 0x0a are read.
If the connection isn't dropped at this point, go to the data framing
section.
3.2. Handshake details
The previous section ignores the data that is transmitted by the
client during the handshake.
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The data sent by the client consists of a number of fields separated
by CR LF pairs (bytes 0x0d 0x0a).
The first field consists of three tokens separated by space
characters (byte 0x20). The middle token is the path being opened.
If the server supports multiple paths, then the server should echo
the value of this field in the initial handshake, as part of the URL
given on the |WebSocket-Location| line (after the appropriate scheme
and host).
The remaining fields consist of name-value pairs, with the name part
separated from the value part by a colon and a space (bytes 0x3a
0x20). Of these, several are interesting:
Host (bytes 48 6f 73 74)
The value gives the hostname that the client intended to use when
opening the Web Socket. It would be of interest in particular to
virtual hosting environments, where one server might serve
multiple hosts, and might therefore want to return different data.
The right host has to be output as part of the URL given on the
|WebSocket-Location| line of the handshake described above, to
verify that the server knows that it is really representing that
host.
Origin (bytes 4f 72 69 67 69 6e)
The value gives the scheme, hostname, and port (if it's not the
default port for the given scheme) of the page that asked the
client to open the Web Socket. It would be interesting if the
server's operator had deals with operators of other sites, since
the server could then decide how to respond (or indeed, _whether_
to respond) based on which site was requesting a connection.
If the server supports connections from more than one origin, then
the server should echo the value of this field in the initial
handshake, on the |WebSocket-Origin| line.
Other fields
Other fields can be used, such as "Cookie" or "Authorization", for
authentication purposes.
3.3. Data framing
NOTE: This section only describes how to handle content that this
specification allows user agents to send (text). It doesn't handle
any arbitrary content in the same way that the requirements on user
agents defined earlier handle any content including possible future
extensions to the protocols.
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The server should run through the following steps to process the
bytes sent by the client:
1. Read a byte from the client. Assuming everything is going
according to plan, it will be a 0x00 byte. Behaviour for the
server is undefined if the byte is not 0x00.
2. Let /raw data/ be an empty byte array.
3. _Data_: Read a byte, let /b/ be that byte.
4. If /b/ is not 0xff, then append /b/ to /raw data/ and return to
the previous step (labeled _data_).
5. Interpret /raw data/ as a UTF-8 string, and apply whatever
server-specific processing should occur for the resulting string.
6. Return to the first step to read the next byte.
The server should run through the following steps to send strings to
the client:
1. Send a 0x00 byte to the client to indicate the start of a string.
2. Encode /data/ using UTF-8 and send the resulting byte stream to
the client.
3. Send a 0xff byte to the client to indicate the end of the
message.
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4. Closing the connection
To *close the Web Socket connection*, either the user agent or the
server closes the TCP/IP connection. There is no closing handshake.
Whether the user agent or the server closes the connection, it is
said that the *Web Socket connection is closed*.
Servers may close the Web Socket connection whenever desired.
User agents should not close the Web Socket connection arbitrarily.
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5. Security considerations
** ISSUE ** ...
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6. IANA considerations
** ISSUE ** ...(two URI schemes, two ports, HTTP Upgrade keyword)
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7. Normative References
[HTML5] Hickson, I., "HTML5", February 2009.
[RFC2109] Kristol, D. and L. Montulli, "HTTP State Management
Mechanism", RFC 2109, February 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.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2965] Kristol, D. and L. Montulli, "HTTP State Management
Mechanism", RFC 2965, October 2000.
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Author's Address
Ian Hickson
Google, Inc.
Email: ian@hixie.ch
URI: http://ln.hixie.ch/
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