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          INTERNET DRAFT                                          S. Barber
          Expires: January 7, 1999               Academ Consulting Services
                                                                August 1998
          
                           Network News Transport Protocol
          
                           draft-ietf-nntpext-base-06.txt
          
          1. Status of this Document
          
            This document is an Internet-Draft. Internet-Drafts are
            working documents of the Internet Engineering Task Force
            (IETF), its areas, and its working groups.  Note that other
            groups may also distribute working documents as Internet-
            Drafts.
          
            Internet-Drafts are draft documents valid for a maximum of six
            months and may be updated, replaced, or made obsolete by other
            documents at any time.  It is inappropriate to use Internet-
            Drafts as reference material or to cite them other than as
            "work in progress."
          
          
            To learn the current status of any Internet-Draft, please
            check the "1id-abstracts.txt" listing contained in the
            Internet-Drafts Shadow Directories on ftp.is.co.za (Africa),
            nic.nordu.net (Europe), munnari.oz.au (Pacific Rim),
            ftp.ietf.org (US East Coast), or ftp.isi.edu (US West
            Coast).
          
            This document is a product of the NNTP Working Group, chaired
            by Ned Freed and Stan Barber.
          
          
          
          2.  Abstract
            The Network News Transport Protocol has been in use in the
            Internet for a decade and remains one of the most popular
            protocols (by volume) in use today. This document is a
            replacement for RFC 977 and officially updates the protocol
            specification. It clarifies some vagueness in RFC 977,
            includes some new base functionality and provides a specific
            mechanism to add standardized extensions to NNTP.
          
          
          3. Introduction
            This document specifies the Network News Transport Protocol
            (NNTP), which is used for the distribution, inquiry,
            retrieval, and posting of net news articles using a reliable
            stream-based mechanism. For news reading clients, NNTP enables
            retrieval of news articles that are stored in a central
            database, giving subscribers the ability to select only those
            articles they wish to read.
          
            The netnews model provides for indexing, cross-referencing,
            and expiration of aged messages. For server-to-server
            interaction, NNTP is designed for efficient transmission of
          
          
          Barber                                              [Page 1]
          

          INTERNET DRAFT                                   August 1998
          
          
            net news articles over a reliable full duplex communication
            method.
          
            Every attempt is made to insure that the protocol
            specification in this document is compatible with the version
            specified in RFC 977[1]. However, this version does not
            support the ill-defined SLAVE command and permits four digit
            years to be specified in the NEWNEWS and NEWGROUPS commands.
            It changes the default character set to UTF-8[2] instead of
            US-ASCII[3]. It also extends the newsgroup name matching
            capabilities already documented in RFC 977.
          
            Generally, new functionality is available using new keywords.
            Part of that new functionality involves a mechanism to
            discover what new functionality is available to clients from a
            server.
          
            This mechanism can also be used to add more functionality as
            needs merit such additions.
          
            The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
            NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
            "OPTIONAL" in this document are to be interpreted as described
            in RFC 2119[4].
          
            An implementation is not compliant if it fails to satisfy one
            or more of the MUST requirements for this protocol.  An
            implementation that satisfies all the MUST and all the SHOULD
            requirements for its protocols is said to be "unconditionally
            compliant"; one that satisfies all the MUST requirements but
            not all the SHOULD requirements for NNTP is said to be
            "conditionally compliant".
          
            For the remainder of this memo, the term "client host" refers
            to a host making use of the NNTP service, while the term
            "server host" refers to a host that offers the NNTP service.
            In addition, where examples of interactions between a client
            host and a server host are provided a "[C]" will be used to
            represent the client host and a "[S]" will be used to
            represent the server host.
          
          
          
          4. Basic Operation.
          
          
            Every NNTP session MUST involve the following in this order:
          
            CONNECTION
            GREETING
            DISCONNECTION
          
            Other steps may occur between the GREETING and DISCONNECTION
            step. They are:
          
          
          Barber                                                 [Page 2]
          

          INTERNET DRAFT                                   August 1998
          
          
            CAPABILITIES DISCOVERY
            NEWS EXCHANGE
            CONCLUSION
          
            NNTP operates over any reliable data stream 8-bit-wide
            channel. When running over TCP/IP, the official port for the
            NNTP service is 119. Initially, the server host starts the
            NNTP service by listening on a TCP port.  When a client host
            wishes to make use of the service, it MUST establish a TCP
            connection with the server host by connecting to that host on
            the same port on which the server is listening. This is the
            CONNECTION step.  When the connection is established, the NNTP
            server host MUST send a greeting. This is the GREETING step.
            The client host and server host SHOULD then exchange commands
            and responses (respectively) until the connection is closed or
            aborted. This final step is called the DISCONNECTION step.
          
            If there is a CONCLUSION step, it MUST immediately precede the
            DISCONNECTION step. There MUST be only one CONNECTION,
            CONCLUSION and DISCONNECTION step for each NNTP session. All
            other steps MAY be repeated as needed.
          
            The character set for all NNTP commands is UTF-8. Commands in
            the NNTP MUST consist of an US-ASCII case-insensitive keyword,
            which MAY be followed by one or more arguments.  An US-ASCII
            CRLF pair MUST terminate all commands. Multiple commands MUST
            NOT be permitted on the same line. Keywords MUST consist of
            printable US-ASCII characters.  Unless otherwise noted
            elsewhere in this document, Arguments SHOULD consist of
            printable US-ASCII characters. Keywords and arguments MUST be
            each separated by one or more US-ASCII SPACE or US-ASCII TAB
            characters. Keywords MUST be at least three US-ASCII
            characters and MUST NOT exceed 12 US-ASCII characters.
            Command lines MUST NOT exceed 512 octets, which includes the
            terminating US-ASCII CRLF pair. Arguments must not exceed 497
            octets.
          
            Each response MUST start with a three-digit status indicator
            that is sufficient to distinguish all responses. Responses to
            certain commands MAY be multi-line. In these cases, which are
            clearly indicated below, after sending the first line of the
            response and an US-ASCII CRLF, any additional lines are sent,
            each terminated by an US-ASCII CRLF pair. When all lines of
            the response have been sent, a final line MUST be sent,
            consisting of a termination octet (US-ASCII decimal code 046,
            ".") and an US-ASCII CRLF pair.  If any line of the multi-line
            response begins with the termination octet, the line MUST be
            "byte-stuffed" by pre-pending the termination octet to that
            line of the response. Hence, a multi-line response is
            terminated with the five octets "CRLF.CRLF" (in US-ASCII).
            When examining a multi-line response, the client MUST check to
            see if the line begins with the termination octet. If so and
            if octets other than US-ASCII CRLF follow, the first octet of
            the line (the termination octet) MUST be stripped away.  If so
          
          
          Barber                                                 [Page 3]
          

          INTERNET DRAFT                                   August 1998
          
          
            and if US-ASCII CRLF immediately follows the termination
            character, then the response from the NNTP server is ended and
            the line containing ".CRLF" (in US-ASCII) MUST NOT considered
            part of the multi-line response.
          
            A NNTP server MAY have an inactivity autologout timer. Such a
            timer MUST be of at least three minutes duration.  The receipt
            of any command from the client during that interval should
            suffice to reset the autologout timer.  When the timer
            expires, the server should close the TCP connection without
            sending any response to the client.
          
          
          
          4.1  Responses Codes
          
            Each response MUST begin with a three-digit response code.
            These are status reports from the server and indicate the
            response to the last command received from the client.
          
            The first digit of the response broadly indicates the success,
            failure, or progress of the previous command.
          
            1xx - Informative message
            2xx - Command ok
            3xx - Command ok so far, send the rest of it.
            4xx - Command was correct, but couldn't be performed for some
               reason.
            5xx - Command unimplemented, or incorrect, or a serious
               program error occurred.
            The next digit in the code indicates the function response
            category.
          
            x0x - Connection, setup, and miscellaneous messages
            x1x - Newsgroup selection
            x2x - Article selection
            x3x - Distribution functions
            x4x - Posting
            x8x - Nonstandard (private implementation) extensions
            x9x - Debugging output
          
            The exact response codes that MUST be expected from each
            command are detailed in the description of the keyword that is
            the first part of the command. In addition, below is listed a
            general set of response codes that MAY be received at any
            time.
          
            Certain status responses contain parameters such as numbers
            and names. In those cases, the number and type of such
            parameters MUST be fixed for each response code to simplify
            interpretation of the response. In all other cases, the client
            MUST only use the response code itself to determine the nature
            of the response.
          
          
          
          Barber                                                 [Page 4]
          

          INTERNET DRAFT                                   August 1998
          
          
            Parameters MUST be separated from the numeric response code
            and from each other by a single US-ASCII space. All numeric
            parameters MUST be in base 10 (decimal) format, and may have
            leading zeros. All string parameters MUST begin after the
            separating space, and MUST end before the following separating
            space or the US-ASCII CRLF pair at the end of the line.
            (Therefore, string parameters MUST NOT contain US-ASCII
            spaces.) All text, if any, in the response which is not a
            parameter of the response must follow and be separated from
            the last parameter by an US-ASCII space.  Also, note that the
            text following a response number may vary in different
            implementations of the server. The 3-digit numeric code should
            be used to determine what response was sent.
          
            Response codes not specified in this standard MAY be used for
            any installation-specific additional commands also not
            specified. These SHOULD be chosen to fit the pattern of x8x
            specified above. (Note that debugging is provided for
            explicitly in the x9x response codes.)
          
            The use of unspecified response codes for a standard command
            is prohibited.
          
            The response pattern x9x is provided for debugging.  Since
            much debugging output may be classed as "informative
            messages", it MUST be the case that responses 190 through 199
            WILL be used for various debugging outputs.  There is no
            requirement in this specification for debugging output.
            However, if such is provided over the connected stream, it
            MUST use these response codes.  If appropriate to a specific
            implementation, other x9x codes MAY be used for debugging.
            (For example, response code 290 could be used to acknowledge a
            remote debugging request.)
          
            A server MUST respond to an unrecognized, unimplemented, or
            syntactically invalid command with a negative status indicator
            (response codes of the form 5XX).  A server MUST respond to a
            command issued when the session is in an incorrect state by
            responding with a negative status indicator. This may be from
            either the 4XX or 5XX group as appropriate.
          
          
          
          5. The WILDMAT format
          
            The WILDMAT format[5] was first developed by Rich Salz based
            on the format used in the UNIX "find" command to articulate
            file names. It was developed to provide a uniform mechanism
            for matching patterns in the same manner that the UNIX shell
            matches filenames. Patterns are implicitly anchored at the
            beginning and end of each string when testing for a match.
            There are five pattern-matching operations other than a strict
            one-to-one match between the pattern and the source to be
            checked for a match. The first is an asterisk (*) to match any
          
          
          Barber                                                 [Page 5]
          

          INTERNET DRAFT                                   August 1998
          
          
            sequence of zero or more UTF-8 characters. The second is a
            question mark (?) to match any single UTF-8 character. The
            third specifies a specific set of characters. The set is
            specified as a list of characters, or as a range of characters
            where the beginning and end of the range are separated by a
            minus (or dash) character, or as any combination of lists and
            ranges. The dash can also be included in the set as a
            character it if is the beginning or end of the set. This set
            is enclosed in square brackets. The close square bracket (])
            may be used in a set if it is the first character in the set.
            The fourth operation is the same as the logical not of the
            third operation and is specified the same way as the third
            with the addition of a caret character (^) at the beginning of
            the test string just inside the open square bracket. The final
            operation uses the backslash character to invalidate the
            special meaning of the open square bracket ([), the asterisk,
            backslash or the question mark. Two backslashes in sequence
            will result in the evaluation of the backslash as a character
            with no special meaning.
          
          
          5.1  Examples
          
                 a) [^]-] -- matches any single character other than a
                    close square bracket or a minus sign/dash.
                 b) *bdc  -- matches any string that ends with the string
                    "bdc" including the string "bdc" (without quotes).
                 c) [0-9a-zA-Z] -- matches any single printable
                    alphanumeric ASCII character.
                 d) a??d  --  matches any four character string which
                    begins with a and ends with d.
          
          6. Format for Keyword Descriptions
            On the following pages are descriptions of each keyword
            recognized by the NNTP server and the responses that will be
            returned by those commands. These keywords are grouped by the
            functional step in which they are used.
          
            Each keyword is shown in upper case for clarity, although the
            NNTP server ignores case in the interpretation of commands.
            Any parameters are shown in lower case.  A parameter shown in
            [square brackets] is optional. For example, [GMT] indicates
            that the triglyph GMT may be present or omitted. A parameter
            that may be repeated is followed by an ellipsis. Mutually
            exclusive parameters are separated by a vertical bar (|)
            character. For example, ggg|<message-id> indicates that a
            group name or a <message-id> may be specified, but not both.
            Some parameters may be case or language specific. See RFC
            1036[6] for these details.
          
            In addition, certain commands make use of a pattern for
            selection of multiple news groups. The pattern in all cases is
            based on the WILDMAT format introduced by Rich Salz in 1986.
            Arguments expected to be in wildmat format will be represented
          
          
          Barber                                                 [Page 6]
          

          INTERNET DRAFT                                   August 1998
          
          
            by the string wildmat. This format is discussed in detail in
            section 5 of this memo.
          
          
          7. The GREETING Step
          
          7.1  Initial Connection
          
            There is no keyword presented by the client upon initial
            connection to the server. The server MUST present an
            appropriate response code as a greeting to the client.  This
            response informs the client about what steps the client should
            take to reach the news exchange step.
          
            The server must present a 200 greeting code if the client is
            authorized to post articles though the use of the POST keyword
            on this server.
          
            The server must present a 201 greeting code if the client is
            not authorized to post articles using the POST keyword.
          
            The server must present a 502 greeting code if the client is
            not permitted under any circumstances from interacting with
            the server. The server should immediately close the connection
            with the client after presenting this code.
          
            In all other cases, the server must present a 400 greeting
            code.
          
          
          7.1.1 MODE READER
          
            MODE READER
          
            MODE READER MAY be used by the client to indicate to the
            server that it is a news reading client. This command may be
            entered at any time. The server must present a greeting code
            (as described in section 7.1.1.1) appropriate to the server's
            ability to provide service to this client in this mode.
          
          
          7.1.1.1 Responses
                 200 Hello, you can post
                 201 Hello, you can't post
                 400 Service temporarily unavailable
                 502 Service unavailable
          
          
          8. The CAPABILITIES DISCOVERY Step
          
            A client NNTP supporting NNTP service extensions should query
            a server early in the session for extensions session by
            issuing the LIST EXTENSIONS command. If the NNTP server
            supports the NNTP service extensions it MUST give a successful
          
          
          Barber                                                 [Page 7]
          

          INTERNET DRAFT                                   August 1998
          
          
            response (see section 8.1.1), a failure response (see section
            8.1.2), or an error response (see section 8.1.3). If the NNTP
            server does not support any NNTP service extensions, it MUST
            generate an error response (see section 8.1.4).
          
          
          
          8.1 LIST EXTENSIONS
          
            If successful, the server NNTP MUST respond with code 202. On
            failure, the server NNTP MUST respond with code 503. On error,
            the server NNTP MUST respond with one of codes 400, 402, 500,
            501 and 502.
          
            This command MAY be issued at anytime during a session.  It is
            not required that the client issues this command before
            attempting to make use of any extension. The response
            generated by this command MAY change during a session because
            of other state information (e.g. server administration).
            However, a client NNTP MUST NOT cache (for use in another
            session) any information returned if the LIST EXTENSIONS
            command succeeds. That is, a client NNTP MUST issue the LIST
            EXTENSIONS command at least once during each session to get
            the current and correct information concerning available
            extensions during that session.
          
          
          
          8.1.1 Successful response
          
            If the server NNTP implements and is able to perform the LIST
            EXTENSIONS command, it MUST return code 202.
          
            Text following the return code on the first line of the reply
            is free form, and not interpreted, and has no practical use,
            as this text is not expected to be revealed to end users.  The
            syntax of other reply lines is precisely defined, and if
            present, MUST be exactly as specified.
          
            Each line listing an extension in the extension-listing begins
            with a single space.  That space is not optional, nor does it
            indicate general white space.  This space guarantees that the
            line can never be misinterpreted as the end of the extension-
            listing, but is required even where there is no possibility of
            ambiguity.
          
            Each extension supported must be listed on a separate line to
            facilitate the possible inclusion of parameters supported by
            each extension command.  The extension-label to be used in the
            response to the LIST EXTENSIONS command will be specified as
            each new extension is added to the NNTP command set.  Often it
            will be the name of a new command added; however this is not
            required.  In fact it is not required that a new feature
          
          
          
          Barber                                                 [Page 8]
          

          INTERNET DRAFT                                   August 1998
          
          
            actually add a new command.  Any parameters included are to be
            specified with the definition of the command concerned.
          
            That specification shall also specify how any parameters
            present are to be interpreted.
          
            The extension-label is nominally case sensitive, however the
            definitions of specific labels and parameters specify the
            precise interpretation, and it is to be expected that those
            definitions will usually specify the label in a case
            independent manner.  Where this is done, implementations are
            recommended to use upper case letters when transmitting the
            extension response.
          
            The LIST EXTENISONS command itself is not included in the list
            of features supported, support for the LIST EXTENSIONS command
            is indicated by return of a reply other than a 500 or 502
            reply.
          
            The end of the list is defined by the usual period on a line
            by itself.
          
            A typical example reply to the LIST EXTENSIONS command might
            be a multiline reply of the form:
          
          
          
                    [C] LIST EXTENSIONS
          
                    [S] 202-Extensions supported:
          
                    [S]  OVER
          
                    [S]  PAT
          
                    [S]  LISTGROUP
          
                    [S] .
          
          
          
            The particular extensions shown here are simply examples of
            what may be defined in other places, no particular meaning
            should be attributed to them.  Recall also, that the extension
            names returned are not command names, as such, but simply
            indications that the server possesses some attribute or other.
          
            The order in which the extensions are returned is of no
            importance, NNTP Servers processes are not required to
            implement any particular order, or even to consistently return
            the same order when the command is repeated.
          
          
          
          
          
          Barber                                                 [Page 9]
          

          INTERNET DRAFT                                   August 1998
          
          
          8.1.2 Failure response
          
            If for some reason the server NNTP is unable to list the
            service extensions it supports, it MUST return code 503.
          
            In the case of a failure response, the client NNTP may try the
            extensions either as the need arises or configure itself for
            the basic NNTP functionality defined in this document.
          
          
          
          8.1.3 Error responses from extended servers
          
            If the server NNTP recognizes the LIST EXTENSIONS command, but
            due to various conditions cannot make any extensions available
            to the client at the time the client issued the LIST
            EXTENSIONS command, it MUST return code 402. No list (not even
            an empty one) will be returned.
          
            The client NNTP should configure itself for the basic NNTP
            functionality defined in this document, or issue commands that
            might change the state of the server, or issue the QUIT
            command (see section 10.1) if a particular extension is
            required for the client to properly operate.
          
            If the server NNTP determines that the NNTP service is no
            longer available (e.g., due to imminent system shutdown), it
            must return code 400. Note that this is response code should
            not be generated due to an inactivity timeout as described in
            section 4.
          
            In the case of an error response, the client NNTP should issue
            the QUIT command (see section 10.1).
          
          
          
          8.1.4 Responses from servers without extensions
          
            A server NNTP that conforms to this memo but does not support
            the extensions specified here will not recognize the LIST
            EXTENSIONS command and MUST consequently return code 500 or
            code 501. The server NNTP SHALL stay in the same state after
            returning this code. The client NNTP may try the extensions
            either as the need arises or configure itself for the basic
            NNTP functionality defined in this document.
          
          
          
          8.1.5 Responses from improperly implemented servers
          
            A server NNTP that improperly implements the LIST EXTENSIONS
            command may return an empty list. Clients SHALL accommodate
            this protocol violation and interpret it as a response code
            402.
          
          
          Barber                                                 [Page 10]
          

          INTERNET DRAFT                                   August 1998
          
          
          9. The NEWS EXCHANGE Step
          
            During this step, two basic types of transactions occur:
          
            article retrieval from the server and article posting to the
            server.
          
          
          9.1 Article Retrieval
          
            News reading clients have available a variety of mechanisms to
            retrieve articles via NNTP. The news articles are stored and
            indexed using three types of keys. One key is the message id
            of an article. According to RFC 1036, this identifier should
            be globally unique. Another key is composed of the news group
            name and the article number within that news group. That key
            MUST be unique to a particular server (there will be only one
            article with that number within a particular news group), but
            is not required to be globally unique.  Additionally, because
            the same article can be cross-posted to multiple news groups,
            there may be multiple keys that point to the same article on
            the same server. The final key is the arrival timestamp,
            giving the time that the article arrived at the server.
          
            The server MUST ensure that article numbers are issued in
            order of arrival timestamp; that is, articles arriving later
            MUST have higher numbers than those that arrive earlier. The
            server SHOULD allocate the next sequential unused number to
            each new article.
          
            Article numbers MUST lie between 1 and 4,294,967,295
            inclusive. The client and server SHOULD NOT use leading zeroes
            in specifying article numbers, and MUST NOT use more than 16
            digits. In some situations, the value zero replaces an article
            number to show some special situation. One case involves
            responses to the ARTICLE, STAT, BODY and HEAD commands where a
            <message-id> is specified as the argument. In those cases, the
            "current article pointer" is not changed.
          
          
          9.1.1 Article Retrieval by News Group Name and Article Number
          
            The following commands are used to set the current news group
            name and the "current article pointer" which is used by other
            commands for article retrieval.
          
          
          9.1.1.1 GROUP
          
            GROUP ggg
          
            The required parameter ggg is the name of the news group to be
            selected (e.g. "news.software.b"). A list of valid news groups
          
          
          
          Barber                                                 [Page 11]
          

          INTERNET DRAFT                                   August 1998
          
          
            may be obtained by using the LIST keyword.  See section 9.4
            for more information on the LIST keyword.
          
            The successful selection response will return the article
            numbers of the first and last articles in the group at the
            moment of selection (these numbers are referred to as the
            "reported low water mark" and the "reported high water mark"),
            and an estimate of the number of articles on file in the
            group.
          
            If the group is not empty, the estimate MUST be at least the
            actual number of articles available, and MUST be no greater
            than one more than the difference between the reported low and
            high water marks. (Some implementations will actually count
            the number of articles on file. Others will just subtract the
            low water mark from the high water mark and add one to get an
            estimate.)
          
            If the group is empty, one of the following three situations
            will occur. Clients MUST accept all three cases; servers MUST
            NOT represent an empty group in any other way.
          
          . The high water mark will be one less than the low water mark,
            and the estimated article count will be zero. Servers SHOULD
            use this method to show an empty group. This is the only time
            that the high water mark can be less than the low water mark.
          . All three numbers will be zero.
          . The high water mark is greater than or equal to the low water
            mark; the estimated article count might be zero or non-zero;
            if non-zero, the same requirements apply as for a non-empty
            group.
          
          
            The set of articles in a group may change after the GROUP
            command is carried out. That is:
          
          . articles may be removed from the group;
          . articles may be reinstated in the group with the same article
            number, but those articles MUST have numbers no less than the
            reported low water mark (note that this is a reinstatement of
            the previous article, not a new article reusing the number);
          . new articles may be added with article numbers greater than
            the reported high water mark (if an article that was the one
            with the highest number has been removed, the next new article
            will not have the number one greater than the reported high
            water mark).
            Except when the group is empty and all three numbers are zero,
            whenever a subsequent GROUP command for the same news group is
            issued, either by the same client or a different client, the
            reported low water mark in the response MUST be no less than
            that in any previous response for that news group sent to any
            client. The client may make use of the low water mark to
            remove all remembered information about articles with lower
            numbers, as these will never recur. This includes the
          
          
          
          Barber                                                 [Page 12]
          

          INTERNET DRAFT                                   August 1998
          
          
            situation when the high water mark is one less than the low
            water mark.
          
            No similar assumption can be made about the high water mark,
            as this can decrease if an article is removed, and then
            increase again if it is reinstated or if new articles arrive.
          
            When a valid group is selected by means of this command, the
            internally maintained "current article pointer" MUST be set to
            the first article in the group and the name of the current
            news group MUST be set to the selected news group name.  If an
            invalid group is specified, the previously selected group and
            article MUST remain selected.  If an empty news group is
            selected, the "current article pointer" is in an indeterminate
            state and MUST NOT be used.
          
            The GROUP keyword MUST be used by a client and a successful
            response received before the any other command is used that
            depends on having the "current article pointer" be valid.
          
          
          
          9.1.1.1.1 Responses
          
                 211 n f l s group selected
                 (n = estimated number of articles in group, f = first
                    article number in the group, l = last article number in
                    the group, s = name of the group.)
                 411 no such news group
          
          9.1.1.2   LAST
          
            LAST
          
            The internally maintained "current article pointer" MUST be
            set to the previous article in the current news group.  If
            already positioned at the first article of the news group, an
            error message MUST be returned and the current article MUST
            remain selected.
          
            There MAY be no previous article in the group, although the
            current article number is not the reported low water mark.
            There MUST NOT be a previous article when the current article
            number is the reported low water mark.
          
            Because articles can be removed and added, the results of
            multiple LAST and NEXT commands MAY not be consistent over the
            life of a particular NNTP session.
          
            The internally-maintained "current article pointer" MUST be
            set by this command.
          
          
          
          
          
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            A response indicating the current article number and a
            message-id string MUST be returned. No text is sent in
            response to this command.
          
          
          9.1.1.2.1 Responses
          
                 223 n a article retrieved - request text separately (n =
                    article number, a = unique article id)
                 412 no news group selected
                 420 no current article has been selected
                 422 no previous article in this group
          
          
          9.1.1.3 NEXT
          
            NEXT
          
            The internally maintained "current article pointer" MUST be
            advanced to the next article in the current news group.  If no
            more articles remain in the current group, an error message
            MUST be returned and the current article MUST remain selected.
          
            The internally-maintained "current article pointer" MUST be
            set by this command.
          
            A response indicating the current article number and the
            message-id string MUST be returned.  No text is sent in
            response to this command.
          
          
          
          9.1.1.3.1 Responses
          
                 223 n a article retrieved - request text separately (n =
                    article number, a = unique article id)
                 412 no news group selected
                 420 no current article has been selected
                 421 no next article in this group
          
          
          9.2 Retrieval of Articles and Article Sections
          
            There are two forms to the ARTICLE command (and the related
            BODY, HEAD, and STAT commands), each using a different method
            of specifying which article is to be retrieved. When the
            ARTICLE keyword is followed by a message-id in angle brackets
            ("<" and ">"), the first form of the command MUST be used;
            when a numeric parameter or no parameter is supplied, the
            second form MUST be invoked. In the cases where the argument
            is a message-id, the article number specified in the response
            must be zero. This is one of the special cases described in
            section 9.1.
          
          
          
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            An article, as defined by RFC 1036, consists of two parts: the
            article headers and the article body. When responding to an
            article command, the server returns the entire article
            contents and does not attempt to alter or translate them in
            any way.
          
          
          9.2.1 ARTICLE
          
            ARTICLE [<message-id>|nnn]
          
            This response displays the header, a blank line, then the body
            (text) of the specified article. The optional parameter nnn is
            the numeric id of an article in the current news group and
            SHOULD be chosen from the range of articles provided when the
            news group was selected.  If it is omitted, the current
            article is assumed. Message-id is the message id of an article
            as shown in that article's header.
          
            Please note that the internally-maintained "current article
            pointer" MUST NOT be altered when the message-id argument is
            used. This is both to facilitate the presentation of articles
            that may be referenced within an article being read, and
            because of the semantic difficulties of determining the proper
            sequence and membership of an article which may have been
            posted to more than one news group.
          
            The internally-maintained "current article pointer" MUST be
            set when a valid article number is specified as the argument.
            This includes the case when an article number is implied by
            the use of no argument.
          
            A previously valid article number MAY not remain valid if the
            article has been removed. A previously invalid article number
            MAY become valid if the article has been reinstated, but such
            an article number MUST be no less than the reported low water
            mark for that group.
          
            If there is a valid article to present in a reply to this
            command, a response indicating the current article number (or
            zero when the message-id argument is used), a message-id
            string, and that text is to follow MUST be returned.
          
            The message-id string returned is an identification string
            contained within angle brackets ("<" and ">"), which is
            derived from the header of the article itself.  The Message-ID
            header line (required by RFC 1036) from the article must be
            used to supply this information. If the message-id header line
            is missing from the article, a single digit "0" (zero) should
            be supplied within the angle brackets.
          
            Since the message-id field is unique for each article, it may
            be used by a news reading program to skip duplicate displays
          
          
          
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            of articles that have been posted more than once, or to more
            than one news group.
          
          
          9.2.1.1 Responses
                 220 n <a> article retrieved - head and body follow (n =
                    article number, <a> = message-id)
                 412 no news group has been selected
                 420 no current article has been selected
                 423 no such article number in this group
                 430 no such article found
          
          9.2.2 HEAD
            HEAD [<message-id>|nnn]
          
            This response displays the header of the specified article.
            The optional parameter nnn is the numeric id of an article in
            the current news group and SHOULD be chosen from the range of
            articles provided when the news group was selected.  If it is
            omitted, the current article is assumed. Message-id is the
            message id of an article as shown in that article's header.
          
            Please note that the internally-maintained "current article
            pointer" MUST NOT be altered when the message-id argument is
            used. This is both to facilitate the presentation of articles
            that may be referenced within an article being read, and
            because of the semantic difficulties of determining the proper
            sequence and membership of an article which may have been
            posted to more than one news group.
          
            The internally-maintained "current article pointer" MUST be
            set when a valid article number is specified as the argument.
            This includes the case when an article number is implied by
            the use of no argument.
          
            A previously valid article number MAY not remain valid if the
            article has been removed. A previously invalid article number
            MAY become valid if the article has been reinstated, but such
            an article number MUST be no less than the reported low water
            mark for that group.
          
            If there is a valid article to present in a reply to this
            command, a response indicating the current article number (or
            zero when the message-id argument is used), a message-id
            string, and that text is to follow MUST be returned.
          
            The message-id string returned is an identification string
            contained within angle brackets ("<" and ">"), which is
            derived from the header of the article itself.  The Message-ID
            header line (required by RFC 1036) from the article must be
            used to supply this information. If the message-id header line
            is missing from the article, a single digit "0" (zero) should
            be supplied within the angle brackets.
          
          
          
          Barber                                                 [Page 16]
          

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            Since the message-id field is unique for each article, it may
            be used by a news reading program to skip duplicate displays
            of articles that have been posted more than once, or to more
            than one news group.
          
          
          9.2.2.1 Responses
                 221 n <a> article retrieved - head follows
                 412 no news group has been selected
                 420 no current article has been selected
                 423 no such article number in this group
                 430 no such article found
          
          
          9.2.3 BODY
            BODY [<message-id>|nnn]
          
            This response displays the body (text) of the specified
            article. The optional parameter nnn is the numeric id of an
            article in the current news group and SHOULD be chosen from
            the range of articles provided when the news group was
            selected.  If it is omitted, the current article is assumed.
            Message-id is the message id of an article as shown in that
            article's header.
          
            Please note that the internally-maintained "current article
            pointer" MUST NOT be altered when the message-id argument is
            used. This is both to facilitate the presentation of articles
            that may be referenced within an article being read, and
            because of the semantic difficulties of determining the proper
            sequence and membership of an article which may have been
            posted to more than one news group.
          
            The internally-maintained "current article pointer" MUST be
            set when a valid article number is specified as the argument.
            This includes the case when an article number is implied by
            the use of no argument.
          
            A previously valid article number MAY not remain valid if the
            article has been removed. A previously invalid article number
            MAY become valid if the article has been reinstated, but such
            an article number MUST be no less than the reported low water
            mark for that group.
          
            If there is a valid article to present in a reply to this
            command, a response indicating the current article number (or
            zero when the message-id argument is used), a message-id
            string, and that text is to follow MUST be returned.
          
            The message-id string returned is an identification string
            contained within angle brackets ("<" and ">"), which is
            derived from the header of the article itself.  The Message-ID
            header line (required by RFC 1036) from the article must be
            used to supply this information. If the message-id header line
          
          
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            is missing from the article, a single digit "0" (zero) should
            be supplied within the angle brackets.
          
            Since the message-id field is unique for each article, it may
            be used by a news reading program to skip duplicate displays
            of articles that have been posted more than once, or to more
            than one news group.
          
          
          9.2.3.1 Responses
                 222 n <a> article retrieved - body follows
                 412 no news group has been selected
                 420 no current article has been selected
                 423 no such article number in this group
                 430 no such article found
          
          9.2.4 STAT
            STAT [<message-id>|nnn]
          
            This response returns only status information; no article
            contents are returned. The optional parameter nnn is the
            numeric id of an article in the current news group and SHOULD
            be chosen from the range of articles provided when the news
            group was selected.  If it is omitted, the current article is
            assumed. Message-id is the message id of an article as shown
            in that article's header.
          
            Please note that the internally-maintained "current article
            pointer" MUST NOT be altered when the message-id argument is
            used. This is both to facilitate the presentation of articles
            that may be referenced within an article being read, and
            because of the semantic difficulties of determining the proper
            sequence and membership of an article which may have been
            posted to more than one news group.
          
            The internally-maintained "current article pointer" MUST be
            set when a valid article number is specified as the argument.
            This includes the case when an article number is implied by
            the use of no argument.
          
            A previously valid article number MAY not remain valid if the
            article has been removed. A previously invalid article number
            MAY become valid if the article has been reinstated, but such
            an article number MUST be no less than the reported low water
            mark for that group.
          
            If there is a valid article to present in a reply to this
            command, a response indicating the current article number (or
            zero when the message-id argument is used) and a message-id
            string MUST be returned.
          
            The message-id string returned is an identification string
            contained within angle brackets ("<" and ">"), which is
            derived from the header of the article itself.  The Message-ID
          
          
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            header line (required by RFC 1036) from the article must be
            used to supply this information. If the message-id header line
            is missing from the article, a single digit "0" (zero) should
            be supplied within the angle brackets.
          
            Since the message-id field is unique for each article, it may
            be used by a news reading program to skip duplicate displays
            of articles that have been posted more than once, or to more
            than one news group.
          
          
          9.2.4.1 Responses
                 223 n <a> article retrieved - request text separately
                 412 no news group has been selected
                 420 no current article has been selected
                 423 no such article number in this group
                 430 no such article found
          
          
          9.3 Article Posting
          
            Article posting is done in one of two modes: individual
            article posting from news reading clients and article transfer
            from other news servers.
          
          
          9.3.1 POST
          
            POST
          
            If posting is allowed, response code 340 MUST be returned to
            indicate that the article to be posted should be sent.
            Response code 440 MUST be sent if that posting is prohibited
            for some installation-dependent reason.
          
            If posting is permitted, the article MUST be presented to the
            server by the client in the format specified by RFC 1036. The
            text forming the header and body of the message to be posted
            MUST be sent by the client using the conventions for text
            received from the news server: A single period (".") on a line
            indicates the end of the text, with lines starting with a
            period in the original text having that period doubled during
            transmission.
          
            Following the presentation of the termination sequence by the
            client, the server MUST return a response code indicating
            success or failure of the article transfer.
          
            No attempt shall be made by the server to filter characters,
            fold or limit lines, or otherwise process incoming text. The
            intent is that the server just passes the incoming message to
            be posted to the server installation's news posting software,
            which is not part of this specification.
          
          
          
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          9.3.1.1 Responses
          
                 240 article received ok
                 340 send article to be posted. End with <CR-LF>.<CR-LF>
                 440 posting not allowed
                 441 posting failed
          
          9.3.2 IHAVE
          
            IHAVE <message-id>
          
            The IHAVE command informs the server that the client has an
            article whose id is <message-id>. If the server desires a copy
            of that article, it MUST return a response instructing the
            client to send the entire article. If the server does not want
            the article (if, for example, the server already has a copy of
            it), a response indicating that the article is not wanted MUST
            be returned.
          
            If transmission of the article is requested, the client MUST
            send the entire article, including header and body, in the
            manner specified for text transmission from the server. The
            server MUST return a response code indicating success or
            failure of the transferal of the article.
          
            This function differs from the POST command in that it is
            intended for use in transferring already-posted articles
            between hosts. Normally it will not be used when the client is
            a personal news reading program. In particular, this function
            will invoke the server's news posting program with the
            appropriate settings (flags, options, etc.) to indicate that
            the forthcoming article is being forwarded from another host.
          
            However, the server may elect not to post or forward the
            article if after further examination of the article it deems
            it inappropriate to do so. Reasons for such subsequent
            rejection of an article may include such problems as
            inappropriate news groups or distributions, disk space
            limitations, article lengths, garbled headers, and the like.
            These are typically restrictions enforced by the server host's
            news software and not necessarily the NNTP server itself.
          
          
          9.3.2.1 Responses
          
                 235 article transferred ok
                 335 send article to be transferred.  End with <CR-
                 LF>.<CR-LF>
                 435 article not wanted - do not send it
                 436 transfer failed - try again later
                 437 article rejected - do not try again
          
          
          
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            Because some host news posting software may not be able to
            immediately render status on the whether an article is
            inappropriate for posting or forwarding, an NNTP server MAY
            acknowledge the successful transfer of the article and later
            silently discard it. Thus an NNTP server may return the 235
            acknowledgment code and later discard the received article.
          
          
          
          9.4 The LIST Keyword
          
          
          9.4.1 LIST
          
            LIST [ACTIVE [wildmat]]
          
            The response to the LIST keyword with no parameters returns a
            list of valid news groups and associated information.  Each
            news group is sent as a line of text in the following format:
          
               group last first status
          
            where <group> is the name of the news group, <last> is the
            number of the last known article currently in that news group,
            <first> is the number of the first article currently in the
            news group, and <status> indicates the current status of the
            group on this server. Typically, the <status> will be consist
            of the US-ASCII character `y' where posting is permitted, `n'
            where posting is not permitted and `m' where postings will be
            forwarded to the news group moderator by the news server.
            Other status strings may exist. The definition of these other
            values are covered in other specifications.
          
            The <first> and <last> fields will always be numeric.  They
            may have leading zeros.  If the <last> field evaluates to less
            than the <first> field, there are no articles currently on
            file in the news group.
          
            Note that posting may still be prohibited to a client although
            the LIST command indicates that posting is permitted to a
            particular news group. See the POST command for an explanation
            of client prohibitions. The posting flag exists for each news
            group because some news groups are moderated or are digests,
            and therefore cannot be posted to; that is, articles posted to
            them must be mailed to a moderator who will post them for the
            original poster.  This is independent of the posting
            permission granted to a client by the NNTP server.
          
            Please note that an empty list (i.e., the text body returned
            by this command consists only of the terminating period) is a
            possible valid response, and indicates that there are
            currently no valid news groups.
          
          
          
          
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            If the optional matching parameter is specified, the list is
            limited to only the groups that match the pattern.
          
            Specifying a single group is usually very efficient for the
            server, and multiple groups may be specified by using wildmat
            patterns (described in section 5), not regular expressions.
          
          
          
          9.4.1.1 Responses
                 215 list of news groups follows
          
          9.4.2 LIST ACTIVE.TIMES
          
            LIST ACTIVE.TIMES [wildmat]
          
            The active.times file is maintained by some news transport
            systems to contain information about when and who created a
            particular news group. The format of this file generally
            includes three fields. The first field is the name of the news
            group. The second is the time when this group was created on
            this news server measured in seconds since January 1, 1970.
            The third is the email address of the entity that created the
            news group. When executed, the information is displayed
            following the 215 response. When display is completed, the
            server will send a period on a line by itself. If the
            information is not available, the server will return the 503
            error response.
          
            If the optional matching parameter is specified, the list is
            limited to only the groups that match the pattern.
          
            Specifying a single group is usually very efficient for the
            server, and multiple groups may be specified by using wildmat
            patterns (described in section 5), not regular expression
          
          
          9.4.2.1 Responses
          
                 215 information follows
                 503 program error, function not performed
          
          9.4.3 LIST DISTRIBUTIONS
          
            LIST DISTRIBUTIONS
          
            The distributions file is maintained by some news transport
            systems to contain information about valid values for the
            Distribution: line in a news article header and about what the
            values mean. Each line contains two fields, the value and a
            short explanation on the meaning of the value. When executed,
            the information is displayed following the 215 response. When
            display is completed, the server will send a period on a line
          
          
          
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            by itself. If the information is not available, the server
            will return the 503 error response.
          
          
          
          9.4.3.1 Responses
          
                 215 information follows
                 503 program error, function not performed
          
          9.4.4 LIST DISTRIB.PATS
          
            LIST DISTRIB.PATS
          
            The distrib.pats file is maintained by some news transport
            systems to contain default values for the Distribution: line
            in a news article header when posting to particular news
            groups. This information could be used to provide a default
            value for the Distribution: line in the header when posting an
            article. The information returned contains three fields
            separated by colons. The first column is a weight.  The second
            is a group name or a wildmat pattern that can be used to match
            a group name.  The third is the value of the Distribution:
            line that should be used when the group name matches and the
            weight value is the highest. All this processing is done by
            the news posting client and not by the server itself. The
            server provides this information to the client for it to use
            or ignore as it chooses. When executed, the information is
            displayed following the 215 response.  When display is
            completed, the server will send a period on a line by itself.
            If the information is not available, the server will return
            the 503 error response.
          
          
          
          9.4.4.1 Responses
          
                 215 information follows
                 503 program error, function not performed
          
          9.4.5 LIST NEWSGROUPS
          
               LIST NEWSGROUPS [wildmat]
          
               The newsgroups file is maintained by some news transport
               systems to contain the name of each news group that is
               active on the server and a short description about the
               purpose of each news group. Each line in the file contains
               two fields, the news group name and a short explanation of
               the purpose of that news group. When executed, the
               information is displayed following the 215 response. When
               display is completed, the server will send a period on a
               line by itself. If the information is not available, the
               server will return the 503 response.  If the optional
          
          
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               matching parameter is specified, the list is limited to only
               the groups that match the pattern (no matching is done on
               the group descriptions).  Specifying a single group is
               usually very efficient for the server, and multiple groups
               may be specified by using wildmat patterns (see section 5),
               not regular expressions. If nothing is matched an empty list
               is returned, not an error.
          
          
          
          9.4.5.1 Responses
          
                 215 information follows
                 503 program error, function not performed
          
          9.4.6 LIST OVERVIEW.FMT
          
            LIST OVERVIEW.FMT
          
            The overview.fmt file is maintained by some news transport
            systems to contain the order in which header information is
            stored in the overview databases for each news group.  When
            executed, news article header fields are displayed one line at
            a time in the order in which they are stored in the overview
            database[7] following the 215 response.  When display is
            completed, the server will send a period on a line by itself.
            If the information is not available, the server will return
            the 503 response.
          
            Please note that if the header has the word "full" (without
            quotes) after the colon, the header's name is prepended to its
            field in the output returned by the server.
          
          
          
          9.4.6.1 Responses
          
                 215 information follows
                 503 program error, function not performed
          
          9.4.7 LIST SUBSCRIPTIONS
          
            LIST SUBSCRIPTIONS
          
            This command is used to get a default subscription list for
            new users of this server. The order of groups is significant.
          
            When this list is available, it is preceded by the 215
            response and followed by a period on a line by itself.  When
            this list is not available, the server returns a 503 response
            code.
          
          
          
          
          
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          9.4.7.1 Responses
          
                 215 information follows
                 503 program error, function not performed
          
          9.4.8 LISTGROUP
          
               LISTGROUP [ggg]
          
               The LISTGROUP command is used to get a listing of all the
               article numbers in a particular news group.
          
               The optional parameter ggg is the name of the news group to
               be selected (e.g. "news.software.b").  A list of valid news
               groups may be obtained from the LIST command. If no group is
               specified, the current group is used as the default
               argument.
          
               The successful selection response will be a list of the
               article numbers in the group followed by a period on a line
               by itself.
          
               When a valid group is selected by means of this command, the
               internally maintained "current article pointer" MUST be set
               to the first article in the group.  If an invalid group is
               specified, the previously selected group and article remain
               selected.  If an empty news group is selected, the "current
               article pointer" may be in an indeterminate state and should
               not be used.
          
               The group name MUST match a news group obtained from the
               LIST command or an error will result, else the server will
               response with the 411 error code.
          
          
          
          9.4.8.1 Responses
          
                 211 list of article numbers follow
                 411 No such group
                 412 Not currently in news group
          
          9.4.9 OVER
          
            OVER [range]
          
            The OVER command returns information from the overview
            database for the article(s) specified. The information
            returned in the response to this command can be used by
            clients to follow discussion threads.
          
            The optional range argument may be any of the following:
          
          . an article number
          
          
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          . an article number followed by a dash to indicate all following
          . an article number followed by a dash followed by another
            article number
            If no argument is specified, then information from the current
            article is displayed. Successful responses start with a 224
            response followed by the overview information for all matched
            messages. Once the output is complete, a period is sent on a
            line by itself. If no argument is specified, the information
            for the current article is returned.  A news group must have
            been selected earlier, else a 412 error response is returned.
            If no articles are in the range specified, the server returns
            a 420 error response. A 502 response will be returned if the
            client only has permission to transfer articles.
          
            Each line of output MUST be formatted with the article number,
            followed by each of the headers in the overview database or
            the article itself (when the data is not available in the
            overview database) for that article separated by a US-ASCII
            tab character.  The sequence of fields must be in this order:
            subject, author, date, message-id, references, byte count, and
            line count. Other optional fields may follow line count. These
            fields are specified by examining the response to the LIST
            OVERVIEW.FMT command. Where no data exists, a null field must
            be provided (i.e. the output will have two tab characters
            adjacent to each other). Servers should not output fields for
            articles that have been removed since the overview database
            was created.
          
            Note that all US-ASCII tab characters in any header data that
            is returned will be converted to a single US-ASCII space
            character. A contiguous sequence of US-ASCII non-printing
            characters will be compressed to a single US-ASCII space
            character in any output response.
          
          
          9.4.9.1 Responses
          
                 224 Overview information follows
                 412 No news group current selected
                 420 No article(s) selected
                 502 no permission
          
          
          9.4.10 PAT
          
            PAT header range|<message-id> [pat [pat...]]
          
            The PAT command is used to retrieve specific headers from
            specific articles, based on pattern matching on the contents
            of the header.
          
            The required header parameter is the name of a header line
            (e.g.  "subject") in a news group article. See RFC-1036 for a
          
          
          
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            list of valid header lines. The required range argument may be
            any of the following:
          
          . an article number
          . an article number followed by a dash to indicate all following
          . an article number followed by a dash followed by another
            article number.
            The required message-id argument indicates a specific article.
            The range and message-id arguments are mutually exclusive. If
            there are additional arguments, they are joined together
            separated by a single space to form one complete pattern. If
            there are no additional arguments, a wildmat "*" is the
            default. Successful responses start with a 221 response
            followed by article number, an US-ASCII space, and the header
            from that message in which the pattern matched the contents of
            the specified header line. A valid response includes an empty
            list (indicating that there was no matches). Once the output
            is complete, a period is sent on a line by itself. If the
            optional argument is a message-id and no such article exists,
            the 430 error response shall be returned. A 502 response shall
            be returned if the client only has permission to transfer
            articles.
          
          
          
          
          9.4.10.1 Responses
          
                 221 Header follows
                 430 no such article
                 502 no permission
          
          
          10. The CONCLUSION Step
          
          10.1 QUIT
          
            QUIT
          
            The server process MUST acknowledge the QUIT command and then
            closes the connection to the client.  This is the preferred
            method for a client to indicate that it has finished all its
            transactions with the NNTP server.
          
            If a client simply disconnects (or the connection times out or
            some other fault occurs), the server SHALL gracefully cease
            its attempts to service the client.
          
          
          10.1.1 Responses
          
                 205 closing connection - goodbye!
          
          
          
          
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          11. Other Keywords
          
            There are other Keywords that may be used at any time between
            the beginning of a session and its termination.  Using these
            keywords do not alter any state information, but the response
            generated from the use of these keywords may provide useful
            information to clients that use them.
          
          
          11.1 DATE
          
            DATE
          
            This command exists to help clients find out the current time
            from the server's perspective.  This command should not be
            used as a substitute for NTP[8], but to provide information
            that might be useful when using the NEWNEWS command (see
            section 11.4).
          
            This command returns a one-line response code of 111 followed
            by the UTC (or GMT) date and time on the server in the form
            YYYYMMDDhhmmss.
          
          
          11.1.1 Responses
          
                 111 YYYYMMDDhhmmss
          
          11.2 The HELP Command
          
            HELP
          
            This command provides a short summary of commands that are
            understood by this implementation of the server. The help text
            will be presented as a textual response terminated by a single
            period on a line by itself.
          
            This text is not guaranteed to be in any particular format and
            shall not be used by clients as a replacement for the LIST
            EXTENSIONS command described in section 8.1.
          
          
          
          11.2.1 Responses
          
                 100 help text follows
          
          
          11.3 NEWGROUPS
          
            NEWGROUPS date time [GMT|UTC] [<distributions>]
          
            A list of newsgroups created since <date and time> MUST be
            listed in the same format as the LIST command.
          
          
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            The date is sent as 6 or 8 digits in the format [XX]YYMMDD,
            where XX is the first two digits of the year, YY is the last
            two digits of the year, MM is the two digits of the month
            (with leading zero, if appropriate), and DD is the day of the
            month (with leading zero, if appropriate). If the first two
            digits of the year are not specified, the year is to be taken
            from the current century if YY is smaller than or equal to the
            current year, otherwise the year is from the previous century.
          
            Time must also be specified.  It must be as 6 digits HHMMSS
            with HH being hours in the 24-hour clock 00-23, MM minutes 00-
            59, and SS seconds 00-60, which allows for leap seconds. The
            tokens "GMT" and "UTC" specifies that the date and time are
            given in UTC. If the tokens "GMT" and "UTC" are omitted then
            the date and time are specified in the server's local
            timezone. Note that there is no way within this specification
            of NNTP to establish the server's local timezone.
          
            The optional parameter "distributions" is a list of
            distribution groups, enclosed in angle brackets.  If
            specified, the distribution portion of an article's header
            will be examined for a match with the distribution categories
            listed, and only those articles which have a distribution in
            the list will be listed.  If more than one distribution is to
            be supplied, they must be separated by commas within the angle
            brackets.
          
            Note that an empty list (i.e., the text body returned by this
            command consists only of the terminating period) is a possible
            valid response, and indicates that there are currently no new
            newsgroups.
          
            Clients SHOULD make all queries using GMT/UTC time when
            possible.
          
          
          11.3.1 Responses
          
                 231 list of new newsgroups follows
          
          11.4 NEWNEWS
          
            NEWNEWS newsgroups date time [GMT] [<distributions>]
          
            A list of message-ids of articles posted or received to the
            specified news group since "date" will be listed. The format
            of the listing will be one message-id per line, as though text
            were being sent.  A single line consisting solely of one
            period followed by CR-LF will terminate the list.
          
            Date and time are in the same format as the NEWGROUPS command.
            The newsgroups parameter must be in wildmat format and may
            consist of multiple wildmat constructs separated by an US-
            ASCII comma character.
          
          
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            The optional parameter "distributions" is a list of
            distribution groups, enclosed in angle brackets.  If
            specified, the distribution portion of an article's header
            will be examined for a match with the distribution categories
            listed, and only those articles which have a distribution in
            the list will be listed.  If more than one distribution is to
            be supplied, they must be separated by commas within the angle
            brackets.
          
            Note that an empty list (i.e., the text body returned by this
            command consists only of the terminating period) is a possible
            valid response, and indicates that there is currently no new
            news.
          
            Clients SHOULD make all queries in GMT/UTC time when possible.
          
          
          11.4.1 Responses
          
               230 list of new articles by message-id follows
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          12. Framework for NNTP Extensions
          
            Although NNTP is widely and robustly deployed, some parts of
            the Internet community might wish to extend the NNTP service.
            This memo defines a means whereby an extended NNTP client may
            query the server to determine the service extensions that it
            supports.
          
            It must be emphasized that any extension to the NNTP service
            should not be considered lightly. NNTP's strength comes
            primarily from its simplicity.  Experience with many protocols
            has shown that:
          
            Protocols with few options tend towards ubiquity, whilst
            protocols with many options tend towards obscurity.
          
            This means that each and every extension, regardless of its
            benefits, must be carefully scrutinized with respect to its
            implementation, deployment, and interoperability costs. In
            many cases, the cost of extending the NNTP service will likely
            outweigh the benefit.
          
            Given this environment, the framework for the extensions
            described in this memo consists of:
          
            a)   a mechanism for clients to determine a server's available
               extensions
            b)   a registry of NNTP service extensions
          
            The LIST EXTENSIONS command is described in section 8.1 of
            this memo and is the mechanism for clients to use to determine
            what extensions are available for client use.
          
            The IANA shall maintain a registry of NNTP service extensions.
          
            Associated with each such extension is a corresponding NNTP
            keyword value. Each service extension registered with the IANA
            MUST be defined in an RFC. Such RFCs either must be on the
            standards-track or must define an IESG-approved experimental
            protocol.  The definition must include:
          
          . the textual name of the NNTP service extension;
          . the label that is returned by LIST EXTENSIONS that would
            indicate to the client that the server supports this
            particular extension.
          . any new NNTP keywords associated with the extension;
          . the syntax and possible values of parameters associated with
            the new NNTP keywords;
          . any new parameters the extension associates with any other
            pre-existing NNTP verbs;
          
          
          
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          . how support for the extension affects the behavior of a server
            and client NNTP; and,
          . the increment by which the extension is increasing the maximum
            length of the any commands over that specified in this
            document.
            In addition, any NNTP keyword value that starts with an upper
            or lower case "X" refers to a local NNTP service extension,
            which is used through bilateral, rather than standardized,
            agreement. Keywords beginning with "X" may not be used in a
            registered service extension.
          
            Any keyword values presented in the NNTP response that do not
            begin with "X" must correspond to a standard, standards-track,
            or IESG-approved experimental NNTP service extension
            registered with IANA.  A conforming server must not offer non
            "X" prefixed keyword values that are not described in a
            registered extension.
          
            Additional verbs are bound by the same rules as NNTP keywords;
            specifically, verbs beginning with "X" are local extensions
            that may not be registered or standardized and verbs not
            beginning with "X" must always be registered.
          
          
          
          
          12.1 Initial IANA Registry
          
            The IANA's initial registry of NNTP service extensions
            consists of these entries:
          
          
          Service Extension     NNTP Extension Label  Added Behavior
          
          Overview Support      OVER                  Defined in this
                                                      document
          
          Specific Article      LISTGROUP             Defined in this
          Numbers                                     document
          
          Header Pattern        PAT                   Defined in this
          Matching                                    document
          
          
          
          13. Augmented BNF[9] Syntax for NNTP Commands
          
          This syntax defines the non-terminal "command". The non-terminal
          "parameter" is used for command parameters whose syntax is
          specified elsewhere. The syntax is in alphabetical order. Note
          that ABNF strings are case insensitive.
          
            article-command = "ARTICLE" [1*WSP (msg-id / article-number)]
               *WSP CRLF
          
          
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            article-number = 1*16DIGIT
            augument = parameter ; excluding sequence ".."
            body-command = "BODY" [1*WSP (msg-id / article-number)] *WSP
               CRLF
            command = article-command /
               body-command /
               date-command /
               group-command /
               head-command /
               help-command /
               ihave-command /
               last-command /
               list-active-times-command /
               list-distrib-pats-command /
               list-distributions-command /
               list-extensions-command /
               list-newsgroups-command /
               list-overview-fmt-command /
               list-subscriptions-command /
               list-command /
               listgroup-command /
               mode-reader-command /
               newgroups-command /
               newnews-command /
               next-command /
               over-command /
               pat-command /
               post-command /
               quit-command /
               stat-command
            CR = %x0D
            CRLF = CR LF
            date-command = "DATE" *WSP CRLF
            date = 6*8DIGIT
            DIGIT = %x30-39
            distribution = parameter
            group-command = "GROUP" 1*WSP newsgroup *WSP CRLF
            head-command = "HEAD" [1*WSP (msg-id / article-number)] *WSP
               CRLF
            header = parameter
            help-command = "HELP" *WSP CRLF
            HT = %x09
            ihave-command = "IHAVE" 1*WSP msg-id *WSP CRLF
            last-command = "LAST" *WSP CRLF
            LF = %x0A
            list-active-times-command = "LIST" 1*WSP "ACTIVE.TIMES"
               [1*WSP wildmat] *WSP CRLF
            list-command = "LIST" [1*WSP "ACTIVE" [1*WSP wildmat]] *WSP
               CRLF
            list-distrib-pats-command = "LIST" 1*WSP "DISTRIB.PATS" *WSP
               CRLF
            list-distributions-command = "LIST" 1*WSP "DISTRIBUTIONS" *WSP
               CRLF
            list-extensions-command = "LIST" 1*WSP "EXTENSIONS" *WSP CRLF
          
          
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            list-newsgroups-command = "LIST" 1*WSP "NEWSGROUPS" [1*WSP
               wildmat]
               *WSP CRLF
            list-overview-fmt-command = "LIST" 1*WSP "OVERVIEW.FMT" *WSP
               CRLF
            list-subscriptions-command = "LIST" 1*WSP "SUBSCRIPTIONS" *WSP
               CRLF
            listgroup-command = "LISTGROUP" [1*WSP newsgroup] *WSP CRLF
            mode-reader-command = "MODE" 1*WSP "READER" *WSP CRLF
            msg-id = <defined in RFC822>
            newgroups-command = "NEWGROUPS" 1*WSP date 1*WSP time [1*WSP
               "GMT"/"UTC"][1*WSP "<" distribution *("," distribution)
               ">"] *WSP CRLF
            newnews-command = "NEWNEWS" 1*WSP newsgroup *("," newsgroup)
               1*WSP date 1*WSP time [1*WSP "GMT"/"UTC"]
               [1*WSP "<" distribution *("," distribution) ">"]
               *WSP CRLF
            newsgroup = parameter
            next-command = "NEXT" *WSP CRLF
            over-command = "OVER" [1*WSP range] *WSP CRLF
            parameter = 1*(%x21-FF) ; generic command parameter
            pat-command = "PAT" 1*WSP header 1*WSP (range / msg-id)
               *(1*WSP wildmat) *WSP CRLF
            post-command = "POST" *WSP CRLF
            quit-command = "QUIT" *WSP CRLF
            range = article-number ["-" [article-number]]
            SP = %x20
            stat-command = "STAT" [1*WSP (msg-id / article-number)] *WSP
               CRLF
            time = 6DIGIT
            UTF-8-non-ascii = %xC0-FF 1*(%x80-BF) ; UTF-8 encoding of non-
               ASCII character
            wildmat = 1*("*" / "?" / wildmat-exact / wildmat-set /
            "\" (%x21-7F / UTF-8-non-ascii))
            wildmat-exact = %x21-29 / %x2B-3E / %x40-5A / %x5D-7F / UTF-8-
               non-ascii
            ; exclude space * ? [ \
            wildmat-non-hyphen = %x21-2C / %x2E-7F / UTF-8-non-ascii ;
               exclude space -
            wildmat-set = "[" ["^"] ["]" / "-"] *(wildmat-non-hyphen ["-"
            WSP = SP / HT
          
          
          14. Security Considerations
          
                There are no specific security mechanisms proposed in this standard,
            though such mechanisms may be added via the extensions process.
          
          
          15. References
            1 Kantor, B and P. Lapsley, "Network News Transfer Protocol",
            RFC-977, U.C. San Diego and U.C. Berkeley.
          
            2 Yergeau, F., "UTF-8, a transformation format of Unicode and
            ISO 10646", RFC 2044, Alis Technologies.
          
          
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            3 Coded Character Set-7-bit American Standard Code for
            Information Interchange, ANSI x3.4-1986.
          
            4 Bradner, Scott, "Key words for use in RFCs to Indicate
            Requirement Levels", RFC-2119, Harvard University.
          
            5 Salz, Rich, Manual Page for wildmat(3) from the INN 1.4
            distribution, UUNET Technologies, Revision 1.10, April, 1992.
          
            6 Horton, M.R. and R. Adams, "Standard for interchange of
            USENET messages",  RFC-1036, AT&T Bell Laboratories and Center
            for Seismic Studies, December, 1987.
          
            7 Robertson, Rob, "FAQ: Overview database / NOV General
            Information", ftp://ftp.uu.net/networking/news/nntp/inn/faq-
            nov.Z, January, 1995.
          
            8 Mills, David L., "Network Time Protocol (Version 3),
            Specification, Implementation and Analysis", RFC-1305,
            University of Delaware, March 1992.
          
            9 Crocker, D.  and Overell, P., "Augmented BNF for Syntax
            Specifications: ABNF", RFC-2234, Internet Mail Consortium and
            Demon Internet, Ltd.
          
          16. Notes
          
            DEC is a registered trademark of Compaq Computer Corporation.
          
            UNIX is a registered trademark of the X/Open Consortium.
          
            VMS is a registered trademark of Compaq Equipment Corporation.
          
          
          17. Acknowledgments
          
            The author acknowledges the original authors of NNTP as
            documented in RFC 977: Brian Kantor and Phil Lapsey.
          
            The author gratefully acknowledges the work of the NNTP
            committee chaired by Eliot Lear. The organization of this
            document was influenced by the last available draft from this
            working group. A special thanks to Eliot for generously
            providing the original machine readable sources for that
            document.
          
            The author gratefully acknowledges the work of the Marshall
            Rose & John G. Meyers in RFC 1939 and the work of the DRUMS
            working group, specifically RFC 1869, which is the basis of
            the NNTP extensions mechanism detailed in this document.
          
            The author gratefully acknowledges the comments and additional
            information provided by the following individuals in preparing
            one of the progenitors of this document:
          
          
          
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          . Wayne Davison <davison@armory.com>
          . Clive D.W. Feather <clive@demon.net>
          . Chris Lewis <clewis@bnr.ca>
          . Tom Limoncelli <tal@mars.superlink.net>
          . Eric Schnoebelen <eric@egsner.cirr.com>
          . Rich Salz <rsalz@osf.org>
          
            This work was precipitated by the work of various newsreader
            authors and newsserver authors, which includes those listed
            below:
          
          . Rick Adams -- Original author of the NNTP extensions to the RN
            newsreader and last maintainer of Bnews
          . Stan Barber -- Original author of the NNTP extensions to the
            newsreaders that are part of Bnews.
          . Geoff Collyer -- Original author of the OVERVIEW database
            proposal and one of the original authors of CNEWS
          . Dan Curry -- Original author of the xvnews newsreader
          . Wayne Davision -- Author of the first threading extensions to the
            RN newsreader (commonly called TRN).
          . Geoff Huston -- Original author of ANU NEWS
          . Phil Lapsey -- Original author of the UNIX reference
            implementation
          . Ian Lea -- Maintainer of the TIN newsreader
          . Rich Salz -- Original author of INN
          . Henry Spencer -- One of the original authors of CNEWS
          . Kim Storm -- Original author of the NN newsreader
          
            18. Author's Address
          
            Stan Barber
            P.O. Box 300481
            Houston, Texas, 77230
            Email: <sob@academ.com>
          
            This document expires January 7, 1999.
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          Barber                                                 [Page 36]
          

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