Registered to the Xinu teaching operating system; a historical name with no live protocol.
IANA registers 2020 as xinupageserver, from Xinu, Douglas Comer's teaching operating system at Purdue, whose remote page server used this port. It is a museum registration: no shipping software binds it today. An open 2020 is an application that took the port, or reverse telnet to line 20 on a Cisco terminal server.
Expose with care
Unidentified listener: identify it before allowing it through a firewall.
$ nc -vz TARGET 2020Seen 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.