No IANA registration and no documented service — a blank number.
726 is absent from the IANA registry and listed as "unknown" in Nmap's service database, with one of the lowest observed open-port frequencies in this range. No published protocol, product default, or documented malware uses it. If it is open, it belongs to something configured locally on that host.
Expose with care
Nothing about the port number justifies exposing it; determine the service first.
$ nmap -sV -p 726 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.