$ tcp
Open Port Checker (TCP)
Free, no signup. Runs from our distributed probes — see how your host looks from different parts of the world.
What is a TCP port check?
The check attempts a TCP connection to a host and port and reports whether something is listening and accepting connections.
It's the right test for everything that isn't a website: mail on 25/587, SSH on 22, databases, VPN endpoints, custom APIs — any service where "is the port reachable" is the question.
How to read the results
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openmeans the TCP handshake completed — a service is listening and reachable from that region. -
closedmeans the host answered "nothing listening here": the service is down or you're testing the wrong port. -
filteredor timeout means a firewall dropped the packet silently — common for database ports (on purpose) and for ports some ISPs block (not on purpose).
Questions
FAQ
What's the difference between closed and filtered?
Closed is an active refusal — the host replied. Filtered is silence — something on the path dropped the packet, usually a firewall. Closed means wrong port or stopped service; filtered means look at firewall rules.
Can I check UDP ports?
Not with this tool — UDP has no handshake, so "open" can't be confirmed the same way. This check is TCP only.
Why is the port open from one region and blocked from another?
Geo-restricted firewalls and ISP-level port blocking are region-specific by nature. That's exactly the kind of partial reachability that multiple probes exist to catch.