Port 6000 (X11)

X Window System display :0 (6000 + display number). Modern X servers disable TCP listening by default.

Registered (user) port, 1024-49151 TCP Remote access Do not expose to the internet

What port 6000 is used for

X Window System display :0 (6000 + display number). Modern X servers disable TCP listening by default.

Security: should port 6000 be open?

Do not expose to the internet. An open X server lets attackers capture keystrokes and screenshots. Use ssh -X forwarding instead of exposing 6000.

IANA assignment

Service nameProtoDescriptionAssigneeReference

x11 TCP X Window System (range 6000-6063) Stephen Gildea -

x11 UDP X Window System (range 6000-6063) Stephen Gildea -

Check what is listening on port 6000

Linux: is anything listening on TCP 6000?

sudo ss -tlnp 'sport = :6000'

Linux / macOS: which process owns the port

sudo lsof -nP -i :6000

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':6000 '

Windows (Command Prompt)

netstat -ano | findstr :6000

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 6000 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine

nc -vz -w 5 HOST 6000

From Windows

Test-NetConnection HOST -Port 6000

Block port 6000 in the firewall

ufw

sudo ufw deny 6000/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 6000 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 6000 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 6000' -Direction Inbound -Protocol TCP -LocalPort 6000 -Action Block

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.