Unassigned at IANA; a conventional second Tomcat port when 8080 is taken.
IANA lists the whole 8163–8180 block as Unassigned, so 8180 is unregistered. It is a common offset choice for a Java servlet container that cannot have 8080 — a second Tomcat instance, or one packaged to sit behind Apache httpd. It is also the port the widely used Metasploitable 2 training image leaves open, which is why 8180 turns up in so many teaching materials and scan write-ups.
Expose with care
Application servers on alternate ports commonly still have the manager or admin webapp deployed; check /manager and /host-manager before exposing it.
$ curl -sI --max-time 5 http://TARGET:8180/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.