The first port of IANA's unassigned 7438-7442 block — no registered service at all.
IANA marks 7438 through 7442 unassigned, and Nmap's database has no service name for it either, with an open-port frequency around 0.015%. There is no protocol to expect and no banner to recognise. Anything listening was configured by hand or picked by an application that wanted a free port above 1024.
Expose with care
Judge the service, not the number: resolve the owning process first, since an unregistered port often hides an admin or debug interface someone assumed nobody would find.
$ nmap -Pn -sV -p 7438 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.