Port 6667 (IRC)

Internet Relay Chat, plain text. Networks commonly use 6660-6669 and 7000 too.

Registered (user) port, 1024-49151 TCP Voice, video and chat Meant to face the internet

What port 6667 is used for

Internet Relay Chat, plain text. Networks commonly use 6660-6669 and 7000 too.

Meant to face the internet. Unencrypted; prefer 6697. Outbound IRC from servers is a classic sign of botnet command-and-control.

Service nameProtoDescriptionAssigneeReference

ircu TCP IRCU (range 6665-6669) Brian Tackett -

Linux: is anything listening on TCP 6667?

sudo ss -tlnp 'sport = :6667'

Linux / macOS: which process owns the port

sudo lsof -nP -i :6667

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':6667 '

Windows (Command Prompt)

netstat -ano | findstr :6667

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 6667 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 6667

From Windows

Test-NetConnection HOST -Port 6667

ufw

sudo ufw allow 6667/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 6667 -j ACCEPT

nftables

sudo nft add rule inet filter input tcp dport 6667 accept

Windows Firewall

New-NetFirewallRule -DisplayName 'Allow TCP 6667' -Direction Inbound -Protocol TCP -LocalPort 6667 -Action Allow

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.