One of five ports IANA reserved in 1990s-era block 3367-3371 for a satellite video data link; effectively never seen.
IANA registers 3367-3371 as a single range, satvid-datalnk, "Satellite Video Data Link", to Scott Engel — with no protocol restriction, no RFC, and no public specification. No open-source or mainstream commercial product implements it. Nmap's service-frequency data ranks 3369/tcp near the bottom of what its scans ever find open. If something is listening here it is almost certainly an unrelated application that picked a free high port, not satellite video.
Expose with care
Nothing standard listens here, so an open 3369 is an unidentified service — find the owning process with lsof or ss before deciding anything about it.
$ nmap -Pn -sV -p 3369 TARGETSeen 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.