MSN/Windows Live Messenger's chat protocol — the service is dead, but the port number long outlived it.
IANA registers 1863 as "msnp" for Microsoft, the notification-server port for MSN Messenger and its successor Windows Live Messenger: clients connected here for sign-in, presence, contact lists, and switchboard sessions. Microsoft never published a specification, and the service was retired worldwide in 2013 in favour of Skype, with the China holdout closing in 2014. What kept 1863 alive afterwards is habit — third-party IM software, bots, and proxies that grew up around MSNP kept using the number, and some unrelated services picked it for being memorable.
Expose with care
No legitimate Microsoft service listens here any more, so an open 1863 is some other program that happened to take the port — identify it rather than trusting the name.
$ nc -vz -w 3 TARGET 1863Seen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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Corrections or a missing port? Reply @rimrocksystems.