Port Checker
Test whether a TCP port is open on any public host. Useful for verifying firewall rules, debugging connectivity, and confirming services are running.
What the results mean
- Open — a service is listening and accepted our connection.
- Closed — the host responded with "nothing here" — no service listening, but the host is reachable.
- Filtered — a firewall is silently dropping our traffic. We can't tell whether a service exists.
- Error — something went wrong (host not found, network unreachable).
For the technical detail behind these states, see our guide on what ports are and how they work.