# WHATPORT(6004)

## NAME

port 6004 — X11 display :4 — X display :4 — another slot in the 6000-6063 X Window System range.

Protocol: TCP  
IANA registry

## DESCRIPTION

IANA covers 6004 under the same `x11` assignment as 6000-6063, making it display :4. Hosts reach it when they run several X servers at once: multi-seat desktops, CI runners spawning Xvfb per job, or a VNC host on its fifth display (paired with RFB 5904). Authorization is still xhost or MIT-MAGIC-COOKIE-1, and the protocol is still cleartext.

## EXPOSURE

**Do not expose.** A reachable X display hands an attacker the screen contents and the keyboard. Start the server with `-nolisten tcp` and use SSH X forwarding for remote access.

## CHECK

```sh
xdpyinfo -display TARGET:4
```

## SEE ALSO

- docs — [X.Org — Xserver(1) manual page](https://xorg.freedesktop.org/archive/current/doc/man/man1/Xserver.1.xhtml) (xorg.freedesktop.org)
- iana — [IANA port registry — 6000-6063 (x11)](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=x11) (iana.org)
- docs — [X.Org Server source repository (xorg/xserver)](https://gitlab.freedesktop.org/xorg/xserver) (gitlab.freedesktop.org)

---

HTML: <https://whatport.net/6004/> · JSON: <https://whatport.net/6004.json> · full dataset: <https://whatport.net/ports.json>