Unregistered high port, scanned by default, claimed by nothing documented.
No IANA registration exists for 56737 and none can: RFC 6335 reserves this range for dynamic and private use. Nmap's nmap-services rates it "unknown" at 0.000228, and it sits directly beside 56738 in the same default top-1000 list. The SANS ISC service field is empty; the attributions on that page are unsourced visitor comments and should not be treated as fact. If it is open on your host, the process table is the only authority.
Expose with care
Nothing known, nothing assumed. Name the process before you route traffic to it.
$ sudo lsof -nP -iTCP:56737 -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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Corrections or a missing port? Reply @rimrocksystems.