The manager side of CMOT, the OSI network-management protocol that SNMP beat.
Port 163 is registered as cmip-man, the CMIP-over-TCP manager, with 164 as the agent side. CMOT — CMIP over TCP/IP, RFC 1189 — was the OSI-flavored competitor to SNMP for managing IP networks, and it lost decisively; the RFC itself was later reclassified as historic. Telco OSS systems were the only real deployments, and those are gone or isolated. You will not meet this on a general-purpose network.
Do not expose
A network-management plane with no modern security story. If something is genuinely speaking CMIP, it belongs on an isolated management network.
$ nc -vz TARGET 163Seen 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.