Explicitly unassigned by IANA since 2002, yet it turns up open more often than its neighbours.
The IANA registry carries an explicit "Unassigned" row for 787 dated 2002-10-08, meaning a previous assignment was withdrawn. Nmap labels it "qsc" and records an open-port frequency roughly an order of magnitude above the surrounding unassigned ports, which suggests some product or appliance uses it by convention without ever registering it. No public specification identifies what that is. Treat a listener here as unidentified until fingerprinted.
Expose with care
Comparatively common in scan data but with no documented protocol behind it; find out what the process is before leaving it reachable.
$ nmap -sV -p 787 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.