Registered as an ISO IP signalling port; no public spec and essentially never observed.
IANA lists 1106 as isoipsigport-1, paired with isoipsigport-2 on 1107, for ISO-over-IP signalling. There is no published specification tied to the registration and no widely deployed implementation, and Nmap's dataset almost never finds it open. An open 1106 is best explained by an unrelated program choosing the port.
Expose with care
Identify what is actually listening before deciding anything; the registration tells you nothing useful about the risk.
$ sudo lsof -nP -iTCP:1106 -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.