Unregistered with no documented default service; the nearest assignment is FairCom's 19790.
IANA does not assign 19780 — 19788 is reserved and 19790 is faircom-db, neither of which covers it. Nmap has no name for the port but scans it by default because measured frequency puts it in the top 1000 TCP ports. Nothing widely deployed documents 19780 as a default listener.
Expose with care
Unknown service on a high port. Name the process before you decide what it deserves; unexplained listeners on public interfaces should be closed in the meantime.
$ nmap -Pn -sV -p 19780 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.