Linux Network Administrator Guide, Second Edition

Lines: 2
Message-ID: ‹[email protected]›
NNTP-Posting-Host: localhost
X-Server-Date: 27 Apr 1999 21:51:50 GMT
Body:
Xref: news.vbrew.com junk:2
.

Retrieving an Article Body Only

If, on the other hand, the user decides she does want to read the article, her newsreader needs a way of requesting that the message body be transmitted. The body command is used for this purpose. It operates in much the same way as the head command, except that only the message body is returned:

body 2
222 2 ‹[email protected]› body
This is another test message, please feel free to ignore it too.
.

Reading an Article from a Group

While it is normally most efficient to separately transfer the headers and bodies of selected articles, there are occasions when we are better off transferring the complete article. A good example of this is in applications through which we want to transfer all of the artices in a group without any sort of preselection, such as when we are using an NNTP cache program like leafnode.[134]

Naturally, NNTP provides a means of doing this, and not surprisingly, it operates almost identically to the head command as well. The article command also accepts an article number or message ID as an argument, but returns the whole article including its header:

article 1
220 1 ‹[email protected]› article
Path: news.vbrew.com!not-for-mail
From: [email protected]
Newsgroups: junk
Subject: test message number 1
Date: 26 Apr 1999 22:08:59 GMT
Organization: The Virtual brewery
Lines: 2
Message-ID: ‹[email protected]›
NNTP-Posting-Host: localhost
X-Server-Date: 26 Apr 1999 22:08:59 GMT
Body:
Xref: news.vbrew.com junk:1
This is a test message, please feel free to ignore it.
.

If you attempt to retrieve an unknown article, the server will return a message with an appropriately coded response code and perhaps a readable text message:

article 4
423 Bad article number

We've described how the most important NNTP commands are used in this section. If you're interested in developing software that implements the NNTP protocol, you should refer to the relevant RFC documents; they provide a great deal of detail that we couldn't include here.

Let's now look at NNTP in action through the nntpd server.

Installing the NNTP Server

The NNTP server (nntpd) may be compiled in two ways, depending on the expected load on the news system. There are no compiled versions available, because of some site-specific defaults that are hardcoded into the executable. All configuration is done through macros defined in common/conf.h.

nntpd may be configured as either a standalone server that is started at system boot time from an rc file, or a daemon managed by inetd. In the latter case, you have to have the following entry in /etc/inetd.conf:

nntp stream tcp nowait news /usr/etc/in.nntpd nntpd

The inetd.conf syntax is described in detail in Chapter 12, Important Network Features. If you configure nntpd as standalone, make sure that any such line in inetd.conf is commented out. In either case, you have to make sure the following line appears in /etc/services:

nntp 119/tcp readnews untp # Network News Transfer Protocol

To temporarily store any incoming articles, nntpd also needs a .tmp directory in your news spool. You should create it using the following commands:

# mkdir /var/spool/news/.tmp
# chown news.news /var/spool/news/.tmp

Restricting NNTP Access

Access to NNTP resources is governed by the file nntp_access in /etc/news. Lines in this file describe the access rights granted to foreign hosts. Each line has the following format:

site read|xfer|both|no post|no [! exceptgroups]

If a client connects to the NNTP port, nntpd attempts to obtain the host's fully qualified domain name from its IP address using reverse lookup. The client's hostname and IP address are checked against the site field of each entry in the order in which they appear in the file. Matches may be either partial or exact. If an entry matches exactly, it applies; if the match is partial, it applies only if there is no other match following it that is at least as good. site may be specified in one of the following ways:

Hostname

This is a fully qualified domain name of a host. If this matches the client's canonical hostname literally, the entry applies, and all following entries are ignored.

IP address

This is an IP address in dotted quad notation. If the client's IP address matches this, the entry applies, and