Open Port Checker
Check whether a TCP port is open on any public host, tested from our server so you see it from the public internet. Shows open, closed or filtered with the common service name. Nothing stored.
About port checking
A TCP port is a numbered door on a server where a particular service listens — port 443 for HTTPS, 22 for SSH, 25 for SMTP, 3306 for MySQL, and so on. Checking a port from an outside server tells you whether that service is reachable from the internet, which is useful for confirming a firewall rule, a port-forward or a newly deployed service — and for spotting ports that should not be exposed (databases and admin ports should rarely be open to the world).
More PAYATE tools
Frequently asked questions
What does the port checker do?
It opens a TCP connection from our server to the host and port you enter and reports whether the port is open (something is listening and reachable) or closed/filtered (nothing answered, or a firewall dropped the attempt). Because the test runs from our server, it checks reachability from the public internet, not just your own network.
Open vs closed vs filtered?
Open — the connection succeeded, a service is listening. Closed — the host answered but refused (no service on that port). Filtered — no answer at all within the timeout, usually a firewall silently dropping the packet.
Why was my host blocked?
For safety the checker only tests public hosts. Private, loopback and reserved addresses (e.g. 127.0.0.1, 10.x, 192.168.x, 169.254.x) are refused so the tool cannot be used to probe internal networks.
Why might a port show closed when I know it is open?
The service may be firewalled to allow only certain source IPs, may listen on IPv6 only, or may be temporarily down. A home/office firewall can also block inbound from unknown servers like ours.
Do you store what I check?
No, nothing is stored. To see the IP a domain resolves to use the IP Lookup or the DNS Lookup.