A Retrospect backup client waiting for its backup server to call — still shipping software, common on Macs.
Retrospect is a long-running backup product for macOS, Windows and Linux, and 497 is its IANA-assigned port on both TCP and UDP. The client agent on each protected machine listens here, and the backup server uses the same port — including subnet broadcast and multicast — to discover and reach clients, which is why Retrospect's own firewall guidance says to open 497 TCP and UDP on both ends. On a Mac network it is one of the more common unexpected open ports, because installing the client opens it automatically.
Do not expose
A backup agent reads every file on the machine — anything that can authenticate to it can pull the whole filesystem, so keep it strictly on the backup network.
$ nc -vz -w 3 TARGET 497Seen 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.