Registered to Talarian's messaging middleware; also the old Yahoo Messenger file-transfer port.
IANA lists 5101/tcp as talarian-tcp (5101/udp as talarian-udp), from Talarian's SmartSockets publish/subscribe middleware, a product later absorbed by TIBCO. The port's other well-known historical use was Yahoo Messenger file transfer, and Yahoo Messenger shut down in 2018. Nmap labels it admdog from the same defunct Chili!Soft ASP family as 5100 and 5102. Nothing current owns it.
Expose with care
Identify what is actually listening. A legacy middleware bus on this port typically predates modern authentication and should stay on an internal segment.
$ sudo lsof -nP -iTCP:5101 -sTCP:LISTENSeen 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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