IANA's "QuickObjects secure port" — a vendor name reservation with no public protocol.
7913 is registered as qo-secure, QuickObjects secure port, to an individual assignee (Jonas Bovin); 7914-7931 above it are unassigned. No specification or open implementation accompanies the registration, and Nmap sees the port open on about 0.015% of hosts. "Secure" in the registered name refers to that product's own scheme, not to any standard TLS behaviour you can rely on.
Expose with care
Do not infer encryption from the name — probe the handshake and identify the service before treating the port as safe to expose.
$ openssl s_client -connect TARGET:7913 </dev/null 2>&1 | head -20Seen 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.