Newsgroups and NNTP

A message area becomes a newsgroup when it is given a newsgroup name. Its messages are then also news articles. Newsreaders (Thunderbird, slrn, tin, Pan) read and post them through the BBS's NNTP server, and peer news servers exchange them with it. So a message posted from a modem shows up on INN, and a reply from a newsreader shows up on a 3270.

bbs area newsgroup General bbs.general
bbs area newsgroup General -          ; no longer a newsgroup
bbs news sync                         ; sync with every peer now
bbs news sync upstream                ; or one

; bbs.conf
[news]
hostname = news.example.org    ; this site in Path and Message-IDs
organization = D-Modem BBS
max_article = 64K

[nntp]
address = :563
tls = implicit                 ; or required: STARTTLS before AUTHINFO
cert_file = /etc/bbs/cert.pem
key_file = /etc/bbs/key.pem
read = anyone                  ; or users: log in first
post = yes

[peer upstream]
address = news.example.net:119
tls = starttls
username = bbs
password = secret
groups = bbs.*
accept_from = news.example.net ; may feed us by IHAVE

The server¶

The NNTP server speaks RFC 3977 with the readers' commands (GROUP, LISTGROUP, ARTICLE/HEAD/BODY/STAT, NEXT/LAST, OVER/XOVER, HDR/XHDR, LIST ACTIVE/NEWSGROUPS/OVERVIEW.FMT, NEWNEWS, POST), IHAVE for peers, AUTHINFO USER/PASS (RFC 4643) with the BBS's login, failure delay and throttling, and STARTTLS (RFC 4642). Every message has a Message-ID. A message posted on the BBS is turned into an article (with From, Date, Path, References from the thread it replies to, and MIME UTF-8 text). An article that came from elsewhere is kept exactly as it arrived, and shown on the BBS as text: its poster, subject and body are decoded (quoted-printable, base64, the charset, the text part of a multipart) and cleaned like anything else a caller writes.

Peers¶

The BBS syncs with its peers every interval seconds, and whenever you run bbs news sync:

pull: for each of our newsgroups the peer carries (and groups matches: a wildmat, bbs.*,!bbs.test), the articles after the last one fetched, by OVER and ARTICLE. The first time, only the latest initial of each group.
push: our articles posted since the last push (on the BBS, by a reader, or from another peer, never back to the peer they came from), by IHAVE; a server that refuses IHAVE to us (a reader-only account) gets POST. The first time only records where to start: the history is not dumped on a new peer.
the peer may feed us by IHAVE from the addresses in accept_from; nobody else may use IHAVE. Names there are looked up when the configuration is loaded (at the start and each reload), not on each connection: if a peer's address changes, reload, or list its addresses.

Each article is taken only once (the BBS keeps a history of Message-IDs, including refused ones), and never if this site is already in its Path, so two peers that carry the same group do not loop. It is stored in the first of its newsgroups that this site carries, and this site's name goes at the head of its Path. This was tested against INN 2.7 in both directions: pushing to it, pulling from it, and innxmit feeding the BBS.

Not supported¶

Control messages (cancel, newgroup, rmgroup) are refused rather than acted on, and deleting a message on the BBS does not cancel it elsewhere. A crossposted article lives in only one area here. There is no NEWGROUPS (the sysop creates newsgroups) and no streaming (CHECK/TAKETHIS), which suits a BBS's volume.