2011-10-17 [colin] 3.7.10cvs32

[claws.git] / doc / src / rfc977.txt

Network Working Group                      Brian Kantor (U.C. San Diego)
Request for Comments: 977                   Phil Lapsley (U.C. Berkeley)
                                                           February 1986

                     Network News Transfer Protocol
                                    
                A Proposed Standard for the Stream-Based
                          Transmission of News

Status of This Memo

   NNTP specifies a protocol for the distribution, inquiry, retrieval,
   and posting of news articles using a reliable stream-based
   transmission of news among the ARPA-Internet community.  NNTP is
   designed so that news articles are stored in a central database
   allowing a subscriber to select only those items he wishes to read.
   Indexing, cross-referencing, and expiration of aged messages are also
   provided. This RFC suggests a proposed protocol for the ARPA-Internet
   community, and requests discussion and suggestions for improvements.
   Distribution of this memo is unlimited.

1.  Introduction

   For many years, the ARPA-Internet community has supported the
   distribution of bulletins, information, and data in a timely fashion
   to thousands of participants.  We collectively refer to such items of
   information as "news".  Such news provides for the rapid
   dissemination of items of interest such as software bug fixes, new
   product reviews, technical tips, and programming pointers, as well as
   rapid-fire discussions of matters of concern to the working computer
   professional. News is very popular among its readers.

   There are popularly two methods of distributing such news: the
   Internet method of direct mailing, and the USENET news system.

1.1.  Internet Mailing Lists

   The Internet community distributes news by the use of mailing lists.
   These are lists of subscriber's mailbox addresses and remailing
   sublists of all intended recipients.  These mailing lists operate by
   remailing a copy of the information to be distributed to each
   subscriber on the mailing list.  Such remailing is inefficient when a
   mailing list grows beyond a dozen or so people, since sending a
   separate copy to each of the subscribers occupies large quantities of
   network bandwidth, CPU resources, and significant amounts of disk
   storage at the destination host.  There is also a significant problem
   in maintenance of the list itself: as subscribers move from one job
   to another; as new subscribers join and old ones leave; and as hosts
   come in and out of service.




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1.2.  The USENET News System

   Clearly, a worthwhile reduction of the amount of these resources used
   can be achieved if articles are stored in a central database on the
   receiving host instead of in each subscriber's mailbox. The USENET
   news system provides a method of doing just this.  There is a central
   repository of the news articles in one place (customarily a spool
   directory of some sort), and a set of programs that allow a
   subscriber to select those items he wishes to read.  Indexing,
   cross-referencing, and expiration of aged messages are also provided.

1.3.  Central Storage of News

   For clusters of hosts connected together by fast local area networks
   (such as Ethernet), it makes even more sense to consolidate news
   distribution onto one (or a very few) hosts, and to allow access to
   these news articles using a server and client model.  Subscribers may
   then request only the articles they wish to see, without having to
   wastefully duplicate the storage of a copy of each item on each host.

1.4.  A Central News Server

   A way to achieve these economies is to have a central computer system
   that can provide news service to the other systems on the local area
   network.  Such a server would manage the collection of news articles
   and index files, with each person who desires to read news bulletins
   doing so over the LAN.  For a large cluster of computer systems, the
   savings in total disk space is clearly worthwhile.  Also, this allows
   workstations with limited disk storage space to participate in the
   news without incoming items consuming oppressive amounts of the
   workstation's disk storage.

   We have heard rumors of somewhat successful attempts to provide
   centralized news service using IBIS and other shared or distributed
   file systems.  While it is possible that such a distributed file
   system implementation might work well with a group of similar
   computers running nearly identical operating systems, such a scheme
   is not general enough to offer service to a wide range of client
   systems, especially when many diverse operating systems may be in use
   among a group of clients.  There are few (if any) shared or networked
   file systems that can offer the generality of service that stream
   connections using Internet TCP provide, particularly when a wide
   range of host hardware and operating systems are considered.

   NNTP specifies a protocol for the distribution, inquiry, retrieval,
   and posting of news articles using a reliable stream (such as TCP)
   server-client model. NNTP is designed so that news articles need only


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RFC 977                                                    February 1986
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   be stored on one (presumably central) host, and subscribers on other
   hosts attached to the LAN may read news articles using stream
   connections to the news host.

   NNTP is modelled upon the news article specifications in RFC 850,
   which describes the USENET news system.  However, NNTP makes few
   demands upon the structure, content, or storage of news articles, and
   thus we believe it easily can be adapted to other non-USENET news
   systems.

   Typically, the NNTP server runs as a background process on one host,
   and would accept connections from other hosts on the LAN.  This works
   well when there are a number of small computer systems (such as
   workstations, with only one or at most a few users each), and a large
   central server.

1.5.  Intermediate News Servers

   For clusters of machines with many users (as might be the case in a
   university or large industrial environment), an intermediate server
   might be used.  This intermediate or "slave" server runs on each
   computer system, and is responsible for mediating news reading
   requests and performing local caching of recently-retrieved news
   articles.

   Typically, a client attempting to obtain news service would first
   attempt to connect to the news service port on the local machine.  If
   this attempt were unsuccessful, indicating a failed server, an
   installation might choose to either deny news access, or to permit
   connection to the central "master" news server.

   For workstations or other small systems, direct connection to the
   master server would probably be the normal manner of operation.

   This specification does not cover the operation of slave NNTP
   servers.  We merely suggest that slave servers are a logical addition
   to NNTP server usage which would enhance operation on large local
   area networks.

1.6.  News Distribution

   NNTP has commands which provide a straightforward method of
   exchanging articles between cooperating hosts. Hosts which are well
   connected on a local area or other fast network and who wish to
   actually obtain copies of news articles for local storage might well
   find NNTP to be a more efficient way to distribute news than more
   traditional transfer methods (such as UUCP).


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   In the traditional method of distributing news articles, news is
   propagated from host to host by flooding - that is, each host will
   send all its new news articles on to each host that it feeds.  These
   hosts will then in turn send these new articles on to other hosts
   that they feed.  Clearly, sending articles that a host already has
   obtained a copy of from another feed (many hosts that receive news
   are redundantly fed) again is a waste of time and communications
   resources, but for transport mechanisms that are single-transaction
   based rather than interactive (such as UUCP in the UNIX-world <1>),
   distribution time is diminished by sending all articles and having
   the receiving host simply discard the duplicates.  This is an
   especially true when communications sessions are limited to once a
   day.

   Using NNTP, hosts exchanging news articles have an interactive
   mechanism for deciding which articles are to be transmitted.  A host
   desiring new news, or which has new news to send, will typically
   contact one or more of its neighbors using NNTP.  First it will
   inquire if any new news groups have been created on the serving host
   by means of the NEWGROUPS command.  If so, and those are appropriate
   or desired (as established by local site-dependent rules), those new
   newsgroups can be created.

   The client host will then inquire as to which new articles have
   arrived in all or some of the newsgroups that it desires to receive,
   using the NEWNEWS command.  It will receive a list of new articles
   from the server, and can request transmission of those articles that
   it desires and does not already have.

   Finally, the client can advise the server of those new articles which
   the client has recently received.  The server will indicate those
   articles that it has already obtained copies of, and which articles
   should be sent to add to its collection.

   In this manner, only those articles which are not duplicates and
   which are desired are transferred.













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RFC 977                                                    February 1986
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2.  The NNTP Specification

2.1.  Overview

   The news server specified by this document uses a stream connection
   (such as TCP) and SMTP-like commands and responses.  It is designed
   to accept connections from hosts, and to provide a simple interface
   to the news database.

   This server is only an interface between programs and the news
   databases. It does not perform any user interaction or presentation-
   level functions. These "user-friendly" functions are better left to
   the client programs, which have a better understanding of the
   environment in which they are operating.

   When used via Internet TCP, the contact port assigned for this
   service is 119.

2.2.  Character Codes

   Commands and replies are composed of characters from the ASCII
   character set.  When the transport service provides an 8-bit byte
   (octet) transmission channel, each 7-bit character is transmitted
   right justified in an octet with the high order bit cleared to zero.

2.3.  Commands

   Commands consist of a command word, which in some cases may be
   followed by a parameter.  Commands with parameters must separate the
   parameters from each other and from the command by one or more space
   or tab characters.  Command lines must be complete with all required
   parameters, and may not contain more than one command.

   Commands and command parameters are not case sensitive. That is, a
   command or parameter word may be upper case, lower case, or any
   mixture of upper and lower case.

   Each command line must be terminated by a CR-LF (Carriage Return -
   Line Feed) pair.

   Command lines shall not exceed 512 characters in length, counting all
   characters including spaces, separators, punctuation, and the
   trailing CR-LF (thus there are 510 characters maximum allowed for the
   command and its parameters).  There is no provision for continuation
   command lines.




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2.4.  Responses

   Responses are of two kinds, textual and status.

2.4.1.  Text Responses

   Text is sent only after a numeric status response line has been sent
   that indicates that text will follow.  Text is sent as a series of
   successive lines of textual matter, each terminated with CR-LF pair.
   A single line containing only a period (.) is sent to indicate the
   end of the text (i.e., the server will send a CR-LF pair at the end
   of the last line of text, a period, and another CR-LF pair).

   If the text contained a period as the first character of the text
   line in the original, that first period is doubled.  Therefore, the
   client must examine the first character of each line received, and
   for those beginning with a period, determine either that this is the
   end of the text or whether to collapse the doubled period to a single
   one.

   The intention is that text messages will usually be displayed on the
   user's terminal whereas command/status responses will be interpreted
   by the client program before any possible display is done.

2.4.2.  Status Responses

   These are status reports from the server and indicate the response to
   the last command received from the client.

   Status response lines begin with a 3 digit numeric code which is
   sufficient to distinguish all responses.  Some of these may herald
   the subsequent transmission of text.

   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.






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   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 should be expected from each command
   are detailed in the description of that 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. The number and type of such parameters is fixed for each
   response code to simplify interpretation of the response.

   Parameters are separated from the numeric response code and from each
   other by a single space. All numeric parameters are decimal, and may
   have leading zeros. All string parameters begin after the separating
   space, and end before the following separating space or the CR-LF
   pair at the end of the line. (String parameters may not, therefore,
   contain 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 a 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 standard commands is
   prohibited.

   We have provided a response pattern x9x for debugging.  Since much
   debugging output may be classed as "informative messages", we would
   expect, therefore, that responses 190 through 199 would be used for
   various debugging outputs.  There is no requirement in this
   specification for debugging output, but 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.  (An example might be to use e.g., 290 to acknowledge a
   remote debugging request.)


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RFC 977                                                    February 1986
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2.4.3.  General Responses

   The following is a list of general response codes that may be sent by
   the NNTP server.  These are not specific to any one command, but may
   be returned as the result of a connection, a failure, or some unusual
   condition.

   In general, 1xx codes may be ignored or displayed as desired;  code
   200 or 201 is sent upon initial connection to the NNTP server
   depending upon posting permission; code 400 will be sent when the
   NNTP server discontinues service (by operator request, for example);
   and 5xx codes indicate that the command could not be performed for
   some unusual reason.

      100 help text
      190
        through
      199 debug output

      200 server ready - posting allowed
      201 server ready - no posting allowed

      400 service discontinued

      500 command not recognized
      501 command syntax error
      502 access restriction or permission denied
      503 program fault - command not performed

3.  Command and Response Details

   On the following pages are descriptions of each command recognized by
   the NNTP server and the responses which will be returned by those
   commands.

   Each command is shown in upper case for clarity, although case is
   ignored in the interpretation of commands by the NNTP server.  Any
   parameters are shown in lower case.  A parameter shown in [square
   brackets] is optional.  For example, [GMT] indicates that the
   triglyph GMT may present or omitted.

   Every command described in this section must be implemented by all
   NNTP servers.






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   There is no prohibition against additional commands being added;
   however, it is recommended that any such unspecified command begin
   with the letter "X" to avoid conflict with later revisions of this
   specification.

   Implementors are reminded that such additional commands may not
   redefine specified status response codes.  Using additional
   unspecified responses for standard commands is also prohibited.

3.1.  The ARTICLE, BODY, HEAD, and STAT commands

   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 command is
   followed by a message-id in angle brackets ("<" and ">"), the first
   form of the command is used; when a numeric parameter or no parameter
   is supplied, the second form is invoked.

   The text of the article is returned as a textual response, as
   described earlier in this document.

   The HEAD and BODY commands are identical to the ARTICLE command
   except that they respectively return only the header lines or text
   body of the article.

   The STAT command is similar to the ARTICLE command except that no
   text is returned.  When selecting by message number within a group,
   the STAT command serves to set the current article pointer without
   sending text. The returned acknowledgement response will contain the
   message-id, which may be of some value.  Using the STAT command to
   select by message-id is valid but of questionable value, since a
   selection by message-id does NOT alter the "current article pointer".

3.1.1.  ARTICLE (selection by message-id)

   ARTICLE <message-id>

   Display the header, a blank line, then the body (text) of the
   specified article.  Message-id is the message id of an article as
   shown in that article's header.  It is anticipated that the client
   will obtain the message-id from a list provided by the NEWNEWS
   command, from references contained within another article, or from
   the message-id provided in the response to some other commands.

   Please note that the internally-maintained "current article pointer"
   is NOT ALTERED by this command. This is both to facilitate the
   presentation of articles that may be referenced within an article


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RFC 977                                                    February 1986
Network News Transfer Protocol


   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 newsgroup.

3.1.2.  ARTICLE (selection by number)

   ARTICLE [nnn]

   Displays the header, a blank line, then the body (text) of the
   current or specified article.  The optional parameter nnn is the

   numeric id of an article in the current newsgroup and must be chosen
   from the range of articles provided when the newsgroup was selected.
   If it is omitted, the current article is assumed.

   The internally-maintained "current article pointer" is set by this
   command if a valid article number is specified.

   [the following applies to both forms of the article command.] A
   response indicating the current article number, a message-id string,
   and that text is to follow will 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
   RFC850) 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 with 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 newsgroup.

3.1.3.  Responses

   220 n <a> article retrieved - head and body follow
           (n = article number, <a> = message-id)
   221 n <a> article retrieved - head follows
   222 n <a> article retrieved - body follows
   223 n <a> article retrieved - request text separately
   412 no newsgroup has been selected
   420 no current article has been selected
   423 no such article number in this group
   430 no such article found





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3.2.  The GROUP command

3.2.1.  GROUP

   GROUP ggg

   The required parameter ggg is the name of the newsgroup to be
   selected (e.g. "net.news").  A list of valid newsgroups may be
   obtained from the LIST command.

   The successful selection response will return the article numbers of
   the first and last articles in the group, and an estimate of the
   number of articles on file in the group.  It is not necessary that
   the estimate be correct, although that is helpful; it must only be
   equal to or larger than the actual number of articles on file.  (Some
   implementations will actually count the number of articles on file.
   Others will just subtract first article number from last to get an
   estimate.)

   When a valid group is selected by means of this command, the
   internally maintained "current article pointer" is 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
   newsgroup is selected, the "current article pointer" is in an
   indeterminate state and should not be used.

   Note that the name of the newsgroup is not case-dependent.  It must
   otherwise match a newsgroup obtained from the LIST command or an
   error will result.

3.2.2.  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











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RFC 977                                                    February 1986
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3.3.  The HELP command

3.3.1.  HELP

   HELP

   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.

   3.3.2.  Responses

   100 help text follows

3.4.  The IHAVE command

3.4.1.  IHAVE

   IHAVE <messageid>

   The IHAVE command informs the server that the client has an article
   whose id is <messageid>.  If the server desires a copy of that
   article, it will 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 will be returned.

   If transmission of the article is requested, the client should send
   the entire article, including header and body, in the manner
   specified for text transmission from the server. A response code
   indicating success or failure of the transferral of the article will
   be returned.

   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
   newsreading 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.

   The server may, however, elect not to post or forward the article if
   after further examination of the article it deems it inappropriate to
   do so.  The 436 or 437 error codes may be returned as appropriate to
   the situation.

   Reasons for such subsequent rejection of an article may include such


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   problems as inappropriate newsgroups 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.

3.4.2.  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

   An implementation note:

   Because some host news posting software may not be able to decide
   immediately that an article is inappropriate for posting or
   forwarding, it is acceptable to acknowledge the successful transfer
   of the article and to later silently discard it.  Thus it is
   permitted to return the 235 acknowledgement code and later discard
   the received article.  This is not a fully satisfactory solution to
   the problem.  Perhaps some implementations will wish to send mail to
   the author of the article in certain of these cases.

3.5.  The LAST command

3.5.1.  LAST

   LAST

   The internally maintained "current article pointer" is set to the
   previous article in the current newsgroup.  If already positioned at
   the first article of the newsgroup, an error message is returned and
   the current article remains selected.

   The internally-maintained "current article pointer" is set by this
   command.

   A response indicating the current article number, and a message-id
   string will be returned.  No text is sent in response to this
   command.

3.5.2.  Responses

   223 n a article retrieved - request text separately
           (n = article number, a = unique article id)



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   412 no newsgroup selected
   420 no current article has been selected
   422 no previous article in this group

3.6.  The LIST command

3.6.1.  LIST

   LIST

   Returns a list of valid newsgroups and associated information.  Each
   newsgroup is sent as a line of text in the following format:

      group last first p

   where <group> is the name of the newsgroup, <last> is the number of
   the last known article currently in that newsgroup, <first> is the
   number of the first article currently in the newsgroup, and <p> is
   either 'y' or 'n' indicating whether posting to this newsgroup is
   allowed ('y') or prohibited ('n').

   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
   newsgroup.

   Note that posting may still be prohibited to a client even though the
   LIST command indicates that posting is permitted to a particular
   newsgroup. See the POST command for an explanation of client
   prohibitions.  The posting flag exists for each newsgroup because
   some newsgroups 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 submitter.  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 newsgroups.

3.6.2.  Responses

   215 list of newsgroups follows







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3.7.  The NEWGROUPS command

3.7.1.  NEWGROUPS

   NEWGROUPS date time [GMT] [<distributions>]

   A list of newsgroups created since <date and time> will be listed in
   the same format as the LIST command.

   The date is sent as 6 digits in the format YYMMDD, where 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).  The closest century is assumed as
   part of the year (i.e., 86 specifies 1986, 30 specifies 2030, 99 is
   1999, 00 is 2000).

   Time must also be specified.  It must be as 6 digits HHMMSS with HH
   being hours on the 24-hour clock, MM minutes 00-59, and SS seconds
   00-59.  The time is assumed to be in the server's timezone unless the
   token "GMT" appears, in which case both time and date are evaluated
   at the 0 meridian.

   The optional parameter "distributions" is a list of distribution
   groups, enclosed in angle brackets.  If specified, the distribution
   portion of a new newsgroup (e.g, 'net' in 'net.wombat') will be
   examined for a match with the distribution categories listed, and
   only those new newsgroups which match will be listed.  If more than
   one distribution group is to be listed, they must be separated by
   commas within the angle brackets.

   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 new newsgroups.

3.7.2.  Responses

   231 list of new newsgroups follows












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Network News Transfer Protocol


3.8.  The NEWNEWS command

3.8.1.  NEWNEWS

   NEWNEWS newsgroups date time [GMT] [<distribution>]

   A list of message-ids of articles posted or received to the specified
   newsgroup 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.

   A newsgroup name containing a "*" (an asterisk) may be specified to
   broaden the article search to some or all newsgroups.  The asterisk
   will be extended to match any part of a newsgroup name (e.g.,
   net.micro* will match net.micro.wombat, net.micro.apple, etc). Thus
   if only an asterisk is given as the newsgroup name, all newsgroups
   will be searched for new news.

   (Please note that the asterisk "*" expansion is a general
   replacement; in particular, the specification of e.g., net.*.unix
   should be correctly expanded to embrace names such as net.wombat.unix
   and net.whocares.unix.)

   Conversely, if no asterisk appears in a given newsgroup name, only
   the specified newsgroup will be searched for new articles. Newsgroup
   names must be chosen from those returned in the listing of available
   groups.  Multiple newsgroup names (including a "*") may be specified
   in this command, separated by a comma.  No comma shall appear after
   the last newsgroup in the list.  [Implementors are cautioned to keep
   the 512 character command length limit in mind.]

   The exclamation point ("!") may be used to negate a match. This can
   be used to selectively omit certain newsgroups from an otherwise
   larger list.  For example, a newsgroups specification of
   "net.*,mod.*,!mod.map.*" would specify that all net.<anything> and
   all mod.<anything> EXCEPT mod.map.<anything> newsgroup names would be
   matched.  If used, the exclamation point must appear as the first
   character of the given newsgroup name or pattern.

   The optional parameter "distributions" is a list of distribution
   groups, enclosed in angle brackets.  If specified, the distribution
   portion of an article's newsgroup (e.g, 'net' in 'net.wombat') will
   be examined for a match with the distribution categories listed, and
   only those articles which have at least one newsgroup belonging to


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RFC 977                                                    February 1986
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   the list of distributions will be listed.  If more than one
   distribution group is to be supplied, they must be separated by
   commas within the angle brackets.

   The use of the IHAVE, NEWNEWS, and NEWGROUPS commands to distribute
   news is discussed in an earlier part of this document.

   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 is currently no new news.

3.8.2.  Responses

   230 list of new articles by message-id follows

3.9.  The NEXT command

3.9.1.  NEXT

   NEXT

   The internally maintained "current article pointer" is advanced to
   the next article in the current newsgroup.  If no more articles
   remain in the current group, an error message is returned and the
   current article remains selected.

   The internally-maintained "current article pointer" is set by this
   command.

   A response indicating the current article number, and the message-id
   string will be returned.  No text is sent in response to this
   command.

3.9.2.  Responses

   223 n a article retrieved - request text separately
           (n = article number, a = unique article id)
   412 no newsgroup selected
   420 no current article has been selected
   421 no next article in this group









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RFC 977                                                    February 1986
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3.10.  The POST command

3.10.1.  POST

   POST

   If posting is allowed, response code 340 is returned to indicate that
   the article to be posted should be sent. Response code 440 indicates
   that posting is prohibited for some installation-dependent reason.

   If posting is permitted, the article should be presented in the
   format specified by RFC850, and should include all required header
   lines. After the article's header and body have been completely sent
   by the client to the server, a further response code will be returned
   to indicate success or failure of the posting attempt.

   The text forming the header and body of the message to be posted
   should 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.

   No attempt shall be made by the server to filter characters, fold or
   limit lines, or otherwise process incoming text.  It is our intent
   that the server just pass the incoming message to be posted to the
   server installation's news posting software, which is separate from
   this specification.  See RFC850 for more details.

   Since most installations will want the client news program to allow
   the user to prepare his message using some sort of text editor, and
   transmit it to the server for posting only after it is composed, the
   client program should take note of the herald message that greeted it
   when the connection was first established. This message indicates
   whether postings from that client are permitted or not, and can be
   used to caution the user that his access is read-only if that is the
   case. This will prevent the user from wasting a good deal of time
   composing a message only to find posting of the message was denied.
   The method and determination of which clients and hosts may post is
   installation dependent and is not covered by this specification.

3.10.2.  Responses

   240 article posted ok
   340 send article to be posted. End with <CR-LF>.<CR-LF>
   440 posting not allowed
   441 posting failed



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RFC 977                                                    February 1986
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   (for reference, one of the following codes will be sent upon initial
   connection; the client program should determine whether posting is
   generally permitted from these:) 200 server ready - posting allowed
   201 server ready - no posting allowed

3.11.  The QUIT command

3.11.1.  QUIT

   QUIT

   The server process acknowledges 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 should gracefully cease its attempts
   to service the client.

3.11.2.  Responses

   205 closing connection - goodbye!

3.12.  The SLAVE command

3.12.1.  SLAVE

   SLAVE

   Indicates to the server that this client connection is to a slave
   server, rather than a user.

   This command is intended for use in separating connections to single
   users from those to subsidiary ("slave") servers.  It may be used to
   indicate that priority should therefore be given to requests from
   this client, as it is presumably serving more than one person.  It
   might also be used to determine which connections to close when
   system load levels are exceeded, perhaps giving preference to slave
   servers.  The actual use this command is put to is entirely
   implementation dependent, and may vary from one host to another.  In
   NNTP servers which do not give priority to slave servers, this
   command must nonetheless be recognized and acknowledged.

3.12.2.  Responses

   202 slave status noted


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RFC 977                                                    February 1986
Network News Transfer Protocol


4.  Sample Conversations

   These are samples of the conversations that might be expected with
   the news server in hypothetical sessions.  The notation C: indicates
   commands sent to the news server from the client program; S: indicate
   responses received from the server by the client.

4.1.  Example 1 - relative access with NEXT

   S:      (listens at TCP port 119)

   C:      (requests connection on TCP port 119)
   S:      200 wombatvax news server ready - posting ok

   (client asks for a current newsgroup list)
   C:      LIST
   S:      215 list of newsgroups follows
   S:      net.wombats 00543 00501 y
   S:      net.unix-wizards 10125 10011 y
           (more information here)
   S:      net.idiots 00100 00001 n
   S:      .

   (client selects a newsgroup)
   C:      GROUP net.unix-wizards
   S:      211 104 10011 10125 net.unix-wizards group selected
           (there are 104 articles on file, from 10011 to 10125)

   (client selects an article to read)
   C:      STAT 10110
   S:      223 10110 <23445@sdcsvax.ARPA> article retrieved - statistics
           only (article 10110 selected, its message-id is
           <23445@sdcsvax.ARPA>)

   (client examines the header)
   C:      HEAD
   S:      221 10110 <23445@sdcsvax.ARPA> article retrieved - head
           follows (text of the header appears here)
   S:      .

   (client wants to see the text body of the article)
   C:      BODY
   S:      222 10110 <23445@sdcsvax.ARPA> article retrieved - body
           follows (body text here)
   S:      .

   (client selects next article in group)


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   C:      NEXT
   S:      223 10113 <21495@nudebch.uucp> article retrieved - statistics
           only (article 10113 was next in group)

   (client finishes session)
   C:      QUIT
   S:      205 goodbye.

4.2.  Example 2 - absolute article access with ARTICLE

   S:      (listens at TCP port 119)

   C:      (requests connection on TCP port 119)
   S:      201 UCB-VAX netnews server ready -- no posting allowed

   C:      GROUP msgs
   S:      211 103 402 504 msgs Your new group is msgs
           (there are 103 articles, from 402 to 504)

   C:      ARTICLE 401
   S:      423 No such article in this newsgroup

   C:      ARTICLE 402
   S:      220 402 <4105@ucbvax.ARPA> Article retrieved, text follows
   S:      (article header and body follow)
   S:      .

   C:      HEAD 403
   S:      221 403 <3108@mcvax.UUCP> Article retrieved, header follows
   S:      (article header follows)
   S:      .

   C:      QUIT
   S:      205 UCB-VAX news server closing connection.  Goodbye.

4.3.  Example 3 - NEWGROUPS command

   S:      (listens at TCP port 119)

   C:      (requests connection on TCP port 119)
   S:      200 Imaginary Institute News Server ready (posting ok)

   (client asks for new newsgroups since April 3, 1985)
   C:      NEWGROUPS 850403 020000

   S:      231 New newsgroups since 03/04/85 02:00:00 follow



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RFC 977                                                    February 1986
Network News Transfer Protocol


   S:      net.music.gdead
   S:      net.games.sources
   S:      .

   C:      GROUP net.music.gdead
   S:      211 0 1 1 net.music.gdead Newsgroup selected
           (there are no articles in that newsgroup, and
           the first and last article numbers should be ignored)

   C:      QUIT
   S:      205 Imaginary Institute news server ceasing service.  Bye!

4.4.  Example 4 - posting a news article

   S:      (listens at TCP port 119)

   C:      (requests connection on TCP port 119)
   S:      200 BANZAIVAX news server ready, posting allowed.

   C:      POST
   S:      340 Continue posting; Period on a line by itself to end
   C:      (transmits news article in RFC850 format)
   C:      .
   S:      240 Article posted successfully.

   C:      QUIT
   S:      205 BANZAIVAX closing connection.  Goodbye.

4.5.  Example 5 - interruption due to operator request

   S:      (listens at TCP port 119)

   C:      (requests connection on TCP port 119)
   S:      201 genericvax news server ready, no posting allowed.

           (assume normal conversation for some time, and
           that a newsgroup has been selected)

   C:      NEXT
   S:      223 1013 <5734@mcvax.UUCP> Article retrieved; text separate.

   C:      HEAD
   C:      221 1013 <5734@mcvax.UUCP> Article retrieved; head follows.

   S:      (sends head of article, but halfway through is
           interrupted by an operator request.  The following
           then occurs, without client intervention.)


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RFC 977                                                    February 1986
Network News Transfer Protocol


   S:      (ends current line with a CR-LF pair)
   S:      .
   S:      400 Connection closed by operator.  Goodbye.
   S:      (closes connection)

4.6.  Example 6 - Using the news server to distribute news between
      systems.

   S:      (listens at TCP port 119)

   C:      (requests connection on TCP port 119)
   S:      201 Foobar NNTP server ready (no posting)

   (client asks for new newsgroups since 2 am, May 15, 1985)
   C:      NEWGROUPS 850515 020000
   S:      235 New newsgroups since 850515 follow
   S:      net.fluff
   S:      net.lint
   S:      .

   (client asks for new news articles since 2 am, May 15, 1985)
   C:      NEWNEWS * 850515 020000
   S:      230 New news since 850515 020000 follows
   S:      <1772@foo.UUCP>
   S:      <87623@baz.UUCP>
   S:      <17872@GOLD.CSNET>
   S:      .

   (client asks for article <1772@foo.UUCP>)
   C:      ARTICLE <1772@foo.UUCP>
   S:      220 <1772@foo.UUCP> All of article follows
   S:      (sends entire message)
   S:      .

   (client asks for article <87623@baz.UUCP>
   C:      ARTICLE <87623@baz.UUCP>
   S:      220 <87623@baz.UUCP> All of article follows
   S:      (sends entire message)
   S:      .

   (client asks for article <17872@GOLD.CSNET>
   C:      ARTICLE <17872@GOLD.CSNET>
   S:      220 <17872@GOLD.CSNET> All of article follows
   S:      (sends entire message)
   S:      .




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RFC 977                                                    February 1986
Network News Transfer Protocol


   (client offers an article it has received recently)
   C:      IHAVE <4105@ucbvax.ARPA>
   S:      435 Already seen that one, where you been?

   (client offers another article)
   C:      IHAVE <4106@ucbvax.ARPA>
   S:      335 News to me!  <CRLF.CRLF> to end.
   C:      (sends article)
   C:      .
   S:      235 Article transferred successfully.  Thanks.

   (or)

   S:      436 Transfer failed.

   (client is all through with the session)
   C:      QUIT
   S:      205 Foobar NNTP server bids you farewell.

4.7.  Summary of commands and responses.

   The following are the commands recognized and responses returned by
   the NNTP server.

4.7.1.  Commands

   ARTICLE
   BODY
   GROUP
   HEAD
   HELP
   IHAVE
   LAST
   LIST
   NEWGROUPS
   NEWNEWS
   NEXT
   POST
   QUIT
   SLAVE
   STAT

4.7.2.  Responses

   100 help text follows
   199 debug output



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RFC 977                                                    February 1986
Network News Transfer Protocol


   200 server ready - posting allowed
   201 server ready - no posting allowed
   202 slave status noted
   205 closing connection - goodbye!
   211 n f l s group selected
   215 list of newsgroups follows
   220 n <a> article retrieved - head and body follow 221 n <a> article
   retrieved - head follows
   222 n <a> article retrieved - body follows
   223 n <a> article retrieved - request text separately 230 list of new
   articles by message-id follows
   231 list of new newsgroups follows
   235 article transferred ok
   240 article posted ok

   335 send article to be transferred.  End with <CR-LF>.<CR-LF>
   340 send article to be posted. End with <CR-LF>.<CR-LF>

   400 service discontinued
   411 no such news group
   412 no newsgroup has been selected
   420 no current article has been selected
   421 no next article in this group
   422 no previous article in this group
   423 no such article number in this group
   430 no such article found
   435 article not wanted - do not send it
   436 transfer failed - try again later
   437 article rejected - do not try again.
   440 posting not allowed
   441 posting failed

   500 command not recognized
   501 command syntax error
   502 access restriction or permission denied
   503 program fault - command not performed

4.8.  A Brief Word about the USENET News System

   In the UNIX world, which traditionally has been linked by 1200 baud
   dial-up telephone lines, the USENET News system has evolved to handle
   central storage, indexing, retrieval, and distribution of news.  With
   the exception of its underlying transport mechanism (UUCP), USENET
   News is an efficient means of providing news and bulletin service to
   subscribers on UNIX and other hosts worldwide.  The USENET News




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RFC 977                                                    February 1986
Network News Transfer Protocol


   system is discussed in detail in RFC 850.  It runs on most versions
   of UNIX and on many other operating systems, and is customarily
   distributed without charge.

   USENET uses a spooling area on the UNIX host to store news articles,
   one per file. Each article consists of a series of heading text,
   which contain the sender's identification and organizational
   affiliation, timestamps, electronic mail reply paths, subject,
   newsgroup (subject category), and the like.  A complete news article
   is reproduced in its entirety below.  Please consult RFC 850 for more
   details.

      Relay-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site
      sdcsvax.UUCP
      Posting-Version: version B 2.10.1 6/24/83 SMI; site unitek.uucp
      Path:sdcsvax!sdcrdcf!hplabs!qantel!ihnp4!alberta!ubc-vision!unitek
      !honman
      From: honman@unitek.uucp (Man Wong)
      Newsgroups: net.unix-wizards
      Subject: foreground -> background ?
      Message-ID: <167@unitek.uucp>
      Date: 25 Sep 85 23:51:52 GMT
      Date-Received: 29 Sep 85 09:54:48 GMT
      Reply-To: honman@unitek.UUCP (Hon-Man Wong)
      Distribution: net.all
      Organization: Unitek Technologies Corporation
      Lines: 12

      I have a process (C program) which generates a child and waits for
      it to return.  What I would like to do is to be able to run the
      child process interactively for a while before kicking itself into
      the background so I can return to the parent process (while the
      child process is RUNNING in the background).  Can it be done?  And
      if it can, how?

      Please reply by E-mail.  Thanks in advance.

      Hon-Man Wong











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RFC 977                                                    February 1986
Network News Transfer Protocol


5.  References

   [1]  Crocker, D., "Standard for the Format of ARPA Internet Text
        Messages", RFC-822, Department of Electrical Engineering,
        University of Delaware, August, 1982.

   [2]  Horton, M., "Standard for Interchange of USENET Messages",
        RFC-850, USENET Project, June, 1983.

   [3]  Postel, J., "Transmission Control Protocol- DARPA Internet
        Program Protocol Specification", RFC-793, USC/Information
        Sciences Institute, September, 1981.

   [4]  Postel, J., "Simple Mail Transfer Protocol", RFC-821,
        USC/Information Sciences Institute, August, 1982.

6.  Acknowledgements

   The authors wish to express their heartfelt thanks to those many
   people who contributed to this specification, and especially to Erik
   Fair and Chuq von Rospach, without whose inspiration this whole thing
   would not have been necessary.

7.  Notes

   <1> UNIX is a trademark of Bell Laboratories.























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