Registered to IANA as Event Listener, with no public protocol behind the name.
IANA holds 3017 as event-listener — registered originally as "event_listener" and later given the well-formed name event-listener, so both appear in service tables. There is no reference document, vendor page, or known open implementation, and the port is uncommon in scan data. The generic name attracts confusion: many unrelated applications describe their own callback socket as an event listener without any connection to this assignment.
Expose with care
The name says nothing about what is running — identify the process, because an event-callback socket that accepts arbitrary input is worth reviewing before exposure.
$ sudo lsof -nP -iTCP:3017 -sTCP:LISTENSeen 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.