No IANA registration and no well-known service — whatever answers here is somebody's own application.
IANA has no service name assigned to 9941 in the service-name and port-number registry, and Nmap's service database lists it as unknown, open on roughly 0.015% of scanned hosts. That leaves no protocol you can assume from the number alone. In practice a listener on a port like this is an internal agent, a container port mapping, or an app that grabbed a free high number. Fingerprint the service instead of trusting the port.
Expose with care
An unidentified listener is an unidentified authentication story. Find the process that owns the socket before deciding whether it belongs on a public interface.
$ sudo lsof -nP -iTCP:9941 -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.