Port 6667 IRC
Port 6667 is the community default for IRC, using TCP.
What is port 6667 used for?
Port 6667 is widely used by IRC (TCP), a community convention rather than an IANA assignment. Classic IRC server port (community convention); modern IRC deployments usually prefer TLS on 6697. It sits in the registered range, the block used by databases, application servers and developer tooling. Port conflicts here are common when several local services start at once.
Ports are the transport-layer address a service listens on. A client that wants to reach IRC connects to port 6667. If nothing is listening, the connection is refused. That is why a port conflict appears whenever two processes try to bind the same number.
Use the commands below to confirm whether port 6667 is actually in use before you change firewall rules. Blocking the port stops new inbound traffic at the firewall, but it does not stop a local process from listening, and it does not remove the service from the machine.
Because this number is not IANA-assigned, a different application may legitimately use it on a machine you do not control. Always identify the actual listening process before deciding that the port belongs to this technology.
Browse all Message queues and streaming ports
This port number is not assigned by IANA. The entry documents a widely adopted community convention.
Check and block port 6667
Copy-ready commands for the protocols assigned to this port. Run the check first, then block only what should not be reachable.
Check on Linux
sudo ss -tlpn 'sport = :6667'Check on Windows
Get-NetTCPConnection -LocalPort 6667 -State Listen -ErrorAction SilentlyContinueBlock with UFW
sudo ufw deny 6667/tcpBlock with iptables
sudo iptables -A INPUT -p tcp --dport 6667 -j DROPThese commands are examples for a typical host. Check the listener before you change firewall rules, and persist iptables rules with iptables-save or netfilter-persistent. On Windows, use Windows Defender Firewall or New-NetFirewallRule for persistent blocks. The iptables rules here cover IPv4; mirror them with ip6tables if IPv6 is enabled.
Is port 6667 safe to expose?
This port is not on our curated list of services with a widely exploited profile. Exposure is only safe when the listening service is intended, patched and protected by a firewall. Keep the listening service patched and remove it if unused. A default-deny firewall policy with explicit allow rules is still the safest baseline.
Where port 6667 is usually used
Most traffic on port 6667 falls into these scenarios. The demo below is a safe way to confirm the listener before you change anything.
- Producers publishing events and consumers subscribing to topics or queues.
- Microservices decoupling background work through a broker on port 6667.
- Local development brokers running in Docker with a published port.
Probe the IRC listener
Classic IRC is plaintext; prefer TLS on 6697 and confirm the server banner before authenticating.
nc -vz 127.0.0.1 6667Common problems with port 6667
Connection refused or timed out
Refused usually means the host is reachable but nothing is listening on port 6667. A timeout more often means a firewall drop, a wrong host or a service bound to a different interface.
Port already in use
Find the process holding the port with sudo ss -tlpn 'sport = :6667' or sudo lsof -i :6667. Stop that process or configure it to bind another port; killing it without identifying it can take down a production service.
Firewall rule did not survive a reboot
UFW and Windows Firewall keep rules across restarts. Raw iptables rules do not: save them with iptables-save or the netfilter-persistent package, and re-apply after upgrades that reset the ruleset.
The port is blocked but still reachable
A firewall rule filters inbound traffic; it does not close the listener. Confirm with the check command above and bind the service to 127.0.0.1 when only local clients need it.
Port 6667 at a glance
| Port number | 6667 |
|---|---|
| Service name | IRC |
| Transport protocol | TCP |
| Category | Message queues and streaming |
| Range | Registered port (1024–10000) |
| Risk level | Standard/Low |
| Reference | Community convention (not IANA-assigned) |
| Registry description | Classic IRC server port (community convention); modern IRC deployments usually prefer TLS on 6697 |
| Source | Community convention |
Frequently asked questions
What is port 6667 used for?
Port 6667 (IRC) uses TCP. Classic IRC server port (community convention); modern IRC deployments usually prefer TLS on 6697 (community convention, not an IANA assignment).
How do I check if port 6667 is open?
On Linux run `sudo ss -tlpn 'sport = :6667'`. On Windows run `Get-NetTCPConnection -LocalPort 6667 -State Listen -ErrorAction SilentlyContinue` in PowerShell. If the port is open, the output shows a process listening on port 6667; empty output usually means nothing is bound to it.
How do I block port 6667?
With UFW run `sudo ufw deny 6667/tcp`. With iptables run `sudo iptables -A INPUT -p tcp --dport 6667 -j DROP`. Persist the iptables rules with your distribution's netfilter-persistent or iptables-save tooling so they survive a reboot.
Is port 6667 safe to expose?
This port is not on our curated list of services with a widely exploited profile. Exposure is only safe when the listening service is intended, patched and protected by a firewall. Nevertheless, keep the listening service patched and remove it if unused. A default-deny firewall policy with explicit allow rules is still the safest baseline.
Related ports
Primary data: IANA Service Name and Transport Protocol Port Number Registry. This number is a community convention, not an IANA assignment.
Last reviewed 2026-10-30 · Methodology · About · Privacy