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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 |  
| LIST ACTIVE | List Active 
Newsgroups | 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. |  
| 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. | 
 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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