Unregistered, but long associated with Compaq/HP web-based server management agents — nmap calls it compaqdiag.
49400 sits in the Dynamic/Private range, so it has no IANA assignment. Its one durable association is historical: Nmap's service database names it compaqdiag, "Compaq Web-based management", from the era of Compaq/HP Insight Management agents on ProLiant servers. If you find it open today it is on old server hardware or an appliance descended from that management stack, and it should be identified with a version scan rather than trusted to the name.
Do not expose
Server management agents are an administrative plane on legacy, usually unpatched software; keep them on a management VLAN, never on a public IP.
$ nmap -Pn -sV -p 49400 TARGETSeen 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.