Verify if specific TCP ports (80, 443, 22, 21, 25, 3306) are reachable from the public internet. Diagnose server firewalls and port forwarding setups.
This tool tests whether specific TCP ports on a host are reachable from the public internet — the common application ports like 80 and 443 (web), 22 (SSH), 21 (FTP), 25 (mail) and 3306 (MySQL). It tells you whether a port is open and accepting connections from outside.
That is exactly what you need when diagnosing a firewall or port-forwarding setup: a service that works locally but is unreachable from outside usually means a closed port or a blocking firewall rule. Confirming reachability from the public side isolates the problem.
A security note in the other direction: a database or admin port (like 3306 or 22) that is open to the whole internet is a risk, so this is also useful for checking that ports which should be closed actually are.
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