Registered as MonkeyCom with no published specification — in practice an unidentified high port.
IANA lists 9898 on both TCP and UDP as monkeycom, registered by an individual with no referenced document, and Nmap carries the same name forward. There is no public protocol description, no maintained implementation to point at, and no reason to expect the registered service on a modern network. A listener on 9898 is almost certainly an unrelated application that chose the number; fingerprint it rather than trusting the registry name.
Expose with care
The registry name tells you nothing about what is actually answering. Identify the process before making an exposure decision.
$ sudo lsof -nP -iTCP:9898 -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.