Registered as "issd" with no attribution and no known implementation.
IANA assigns 1600 (TCP and UDP) to "issd", one of a handful of registry entries that carry no contact, no description beyond the name, and no reference. No mainstream software binds it. In practice a round number like 1600 is far more likely to be someone's hand-picked application or test port than anything to do with the registration.
Expose with care
Treat an open 1600 as a locally chosen port of unknown provenance — the registry name gives you no security properties to reason from.
$ nc -vz -w 3 TARGET 1600Seen 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.