56737's neighbour — same story: no registration, no named service.
56738 is in the Dynamic/Private range and therefore unassignable by IANA under RFC 6335. Nmap's nmap-services carries it as "unknown" at 0.000304, marginally above its neighbour 56737, which is why both survive into the default top-1000 TCP set. No public database names an application, protocol, or malware family for it. Adjacent pairs like this often come from one program binding consecutive ports, but no source confirms that here, so it stays a guess and not a finding.
Expose with care
Unidentified listener. Do not open it inbound; identify what binds it and rate that instead.
$ nmap -Pn -sV --version-all -p 56738 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.