No registration, no named service, and more UDP sightings than TCP in Nmap's data.
63331 falls in the range RFC 6335 reserves for dynamic and private use, so IANA has nothing on it. Nmap's nmap-services carries TCP at 0.000380 and UDP at 0.001004, both "unknown", which is why the port appears in a default scan. SANS ISC has an empty service field; the only attribution there is an unsourced visitor comment naming a long-discontinued Microsoft product, which is not verifiable and is not repeated here. What is verifiable is that it is unregistered and unidentified.
Expose with care
An unidentified listener has unknown authentication and unknown encryption. Keep it internal until you know what it is.
$ nmap -Pn -sV --version-all -p 63331 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.