Registered as the DX Message Base Transport Protocol, and almost never seen.
IANA registers 2874 and 2875 to one person as dxmessagebase1 and dxmessagebase2, "DX Message Base Transport Protocol" — a message-base (BBS-style message store) transport. There is no public specification and no widely distributed implementation, and scan datasets show essentially nothing answering here. If 2875 is open on a host you run, the listener is some local application that picked a free port, not this registration.
Expose with care
Nothing standard lives here, so the honest step is to identify the process behind the port before treating it as expected.
$ sudo lsof -nP -iTCP:2875 -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.