Instant Messages

Inter-BBS real-time IM using the Message Send Protocol (MSP,
RFC 1312). Port 18/tcp.

What's the use?

Synchronet, Mystic, ANetBBS and a handful of others all speak MSP.
A sysop pings you live from another BBS; you see a toast in the
web UI (or a >>> message <<< line on terminal) and can reply.

It's a low-friction way to make sure your neighbour is alive without
sending netmail.

Sending

/imsg/send — pick a target from the BBS Directory or type
username@host manually. Up to ~500 chars per message.

Receiving

Inbound MSP arrives on TCP 18. The listener stores it in the
InstantMessage table; the unread badge in the nav shows the
count. /imsg/ is your inbox.

Network reachability

You need TCP 18 reachable from the outside, OR your messages will
arrive but you can't be paged back. /admin/peers/health runs a
self-test against a list of MSP-speaking BBSes.

Encoding

MSP is 8-bit clean; assume CP437 for safety on inbound. Outbound
encodes the textarea content as latin-1 (so CP437-style art going
out doesn't get mangled).