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NNTP Command Extensions
(Page 3 of 4)
NNTP Newsreader Extensions
The second group of extensions defined
by RFC 2980 are the newsreader extensions, which focus primarily
on commands used by newsreader clients in interactions with NNTP servers.
These extensions consist of several new commands as well as significant
enhancements to one important command that was very limited in its functionality
in RFC 977: LIST.
The original LIST command
has no parameters and only allows a client to retrieve the entire list
of newsgroups a server carries. This may have been sufficient when there
were only a few hundred Usenet newsgroups, but there are now tens of
thousands. RFC 2980 defines a number of new variations of the LIST
command, to allow the client much more flexibility in the types of information
the server returns. Table 268
shows the new LIST command variations.
Table 268: NNTP LIST Command Extensions
Command
Code
|
Command
|
Parameters
|
Description
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LIST ACTIVE
|
List Active
Newsgroups
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Newsgroup name
or pattern
|
Provides a list of active newsgroups
on the server. This is semantically the same as the original LIST
command, but the client may provide a newsgroup name or a pattern to
restrict the number of newsgroups returned.
For example, the client can ask for a list of only the newsgroups that
contain football in them.
|
LIST
ACTIVE.TIMES
|
List
Active Newsgroup Creation Times
|
None
|
Prompts the
server to send the client its active.times file, which contains
information about when the newsgroups carried by the server were created.
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LIST DISTRIBUTIONS
|
List Distributions
|
None
|
Causes the server to sent the
client the contents of the distributions file, which shows what
regional distribution strings the server recognizes (for use in the
Distribution header of a message).
|
LIST
DISTRIB.PATS
|
List
Distribution Patterns
|
None
|
Asks the server
for its distribution.pats file, which is like the distributions
file but uses patterns to summarize distribution information for different
newsgroups.
|
LIST NEWSGROUPS
|
List Newsgroups
|
Newsgroup name
or pattern
|
Provides a list of newsgroup
names and descriptions. This differs from LIST ACTIVE in that
only the newsgroup name and description are returned, and not the article
numbers for each newsgroup. It is functionally the same as XGTITLE
(see Table 269)
and is usually employed by a user to locate a newsgroup to be added
to his or her subscribed list.
|
LIST
OVERVIEW.FMT
|
Display
Overview Format
|
None
|
Prompts the
server to display information about the format of its overview
file. See the XOVER command description below for more.
|
LIST SUBSCRIPTIONS
|
Retrieve
Default Subscription List
|
None
|
Asks the server to send the client
a default list of subscribed newsgroups. This is used to set up a new
user with a suggested list of newsgroups. For example, if an organization
has an internal support newsgroup, they could put this group on the
default subscription list so all new users learn about it immediately
when they first start up their newsreader.
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In addition to these changes
to the LIST command, many new newsreader-related command extensions
are defined, which are described in Table 269.
Table 269: NNTP Newsreader Extensions
Command
Code
|
Command
|
Parameters
|
Description
|
LISTGROUP
|
List Article
Numbers In Newsgroup
|
Newsgroup name
|
Causes the server to return a
list of local article numbers for the current messages in the newsgroup.
The server's current article pointer is also set to the first message
in the group.
|
MODE
READER
|
Set
Newsreader Mode
|
None
|
Tells the server
that the device acting as a client is in fact a client newsreader and
not another NNTP server. While technically not requiredall commands
can be sent by any device acting as clientsome servers may be
optimized to respond to newsreader-oriented commands if given this command.
|
XGTITLE
|
Retrieve
Newsgroup Descriptions
|
Newsgroup name
or pattern
|
Used to list the descriptions
for a newsgroup or a set of newsgroups matching a particular text pattern.
This command is functionally the same as the LIST NEWSGROUP command
extension (see Table 268).
It is therefore recommended that XGTITLE no longer be used.
|
XHDR
|
Retrieve
Article Headers
|
Header
name and optionally, either a message ID or a range of article numbers
|
Allows a client
to ask for only a particular header from a set of messages. If only
the header name is provided, the header is returned for all messages
in the current group. Otherwise, the header is provided for the selected
messages.
This extension provides a newsreader client with a more efficient way
of retrieving and displaying important headers in a newsgroup to a user.
|
XINDEX
|
Retrieve
Index Information
|
Newsgroup name
|
Retrieves an index file,
used by the newsreader TIN to improve the efficiency of newsgroup
perusal. TIN now supports the more common overview
format, so the XOVER command is preferred to this one.
|
XOVER
|
Retrieve
Overview Information
|
Article
number or range of article numbers in a newsgroup
|
Retrieves the
overview for an article or set of articles. Servers supporting
this feature maintain a special database for their newsgroups that contains
information about current articles in a format that can be used by a
variety of newsreaders. Retrieving the overview information allows features
like message
threading to be performed more quickly
than if the client had to retrieve the headers of each message and analyze
them manually.
|
XPAT
|
Retrieve
Article Headers Matching A Pattern
|
Header name,
pattern, and either a message ID or a range of article numbers
|
This command is similar to XHDR
in that it allows a particular header to be retrieved for a set of messages.
The difference is that the client can specify a pattern that must be
matched for the header to be retrieved. This allows the client to have
the server search for and return certain messages, such as those with
a subject line indicating a particular type of discussion, rather than
requiring the client to download all the headers and search through
them.
|
XPATH
|
Retrieve
Filename Information
|
Message
ID
|
Allows a client
to ask for the name of the actual file in which a particular message
is stored on the server.
|
XROVER
|
Retrieve
Overview Reference Information
|
Article number
or range of article numbers in a newsgroup
|
Like the XOVER command,
but specifically retrieves information in the References header
for the indicated articles. This is, of course, the header containing
the data needed to create threaded conversations.
|
XTHREAD
|
Retrieve
Threading Information
|
Optional
DBINIT parameter
|
Similar to
XINDEX, but retrieves a special threading information file in
the format used by the newsreader TRN. Like TIN, TRN
now supports the common overview format so XOVER
is preferred to this command.
The DBINIT parameter can be used to check for the existence
of a thread database.
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