No registration, no known service — a rarely-seen port in the private range.
50300 falls above 49151, so it is Dynamic/Private space that RFC 6335 forbids IANA from assigning. Nmap's service database lists it as unknown for both TCP and UDP with a very low frequency, meaning it is genuinely uncommon on internet-wide scans rather than merely unnamed. If you see it open, it belongs to something local and specific, and only the host's process table will tell you what.
Expose with care
Nothing standard lives here, so there is no baseline to compare against; identify the owning process before making any allow decision.
$ sudo lsof -nP -iTCP:50300 -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.