Unassigned by IANA and unnamed in Nmap's table — a top-1000 scan port with no service behind it.
19842 sits in the same unassigned IANA block as 19801 (19791-19997) and has no registration of any kind. Nmap records a nonzero open-frequency for it from internet-wide scanning, so it is included in the default 1000-port scan, but the service column reads 'unknown'. Anything found open here is site-specific: an in-house daemon, a relocated service, or a mapped container port. There is no protocol to describe.
Expose with care
Judge the listener, not the port number. Run a version scan and decide from what actually answers.
$ nmap -Pn -sV -p 19842 --reason 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.