Where Apache actually listened on Mac OS X Server when the Performance Cache sat in front of it on port 80.
Mac OS X Server is widely reported to have run a performance cache on port 80 with the Apache web server itself moved to TCP 16080, so requests that missed the cache went to 16080. Apple's documentation for that arrangement is no longer published, so the architecture is recorded here as received wisdom rather than a citable fact. Nmap still carries the port as osxwebadmin. Apple retired that architecture with the old Server web stack, so today an open 16080 is more often a generic alternate HTTP port than a Mac.
Expose with care
It is a plain HTTP backend that expects a cache or proxy in front of it. Exposed directly it bypasses whatever the front end was doing, and any HTTP app behind it is served in cleartext.
$ curl -sI --max-time 5 http://TARGET:16080/Seen 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.