No IANA registration; a plain unclaimed high port.
IANA has no assignment for 10012, and Nmap's service database lists it as unknown, open on about 0.04% of scanned hosts. Nothing widely deployed defaults here. A listener is an application, agent, or published container port that took the next free number, so identify it by probing rather than by the number.
Expose with care
No registration, no assumed protocol, no assumed authentication. Establish what owns the socket before exposing it.
$ sudo lsof -nP -iTCP:10012 -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.