Unassigned at IANA and not associated with any documented service.
The IANA registry contains no entry for 9673, and Nmap classifies it as unknown with a low observation rate. No standard protocol, vendor default, or well-attested malware uses it. The honest answer to "what runs on 9673" is: whatever you installed. Find the process and work from there.
Expose with care
No known service means no known security posture. Identify it before exposing it.
$ sudo lsof -nP -iTCP:9673 -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.