X Window System display number 5 — inside IANA's 6000-6063 x11 block.
An X server listening for TCP clients uses port 6000 plus its display number, so display :5 is TCP 6005. Modern desktops start the X server with -nolisten tcp (or run Wayland), so nothing binds here unless someone deliberately re-enabled TCP transport. When it is open it is usually a thin client, an X terminal, or a headless Xvfb instance started for CI screenshots. Access is then gated only by whatever xhost/xauth policy the server was started with.
Do not expose
An X server reachable over TCP with xhost + or a leaked MIT-MAGIC-COOKIE-1 lets anyone read the screen, log keystrokes, and inject input; keep X on Unix sockets and forward it over SSH.
$ xdpyinfo -display TARGET:5Seen 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.