RFC du protocole NNTP : commandes
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.
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
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
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
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
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)
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
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
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
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
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
(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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