Port check explained

What open, closed and timed out mean

An open port usually means a service accepted the connection. A closed port means the host responded but no service accepted the connection. A timeout often means a firewall, routing rule or provider policy dropped the traffic. Results can vary depending on where the check is performed from.

Common examples include 80 for HTTP, 443 for HTTPS, 22 for SSH, 25 for SMTP, 587 for mail submission and 3306 for MySQL. Public exposure should be intentional, especially for admin, database and control panel ports.

When to use a port checker

Use port checks after changing firewall rules, launching a web server, configuring a reverse proxy, opening a game server, debugging email delivery, or confirming that a hosting provider allows inbound traffic. A port can be open from one network and blocked from another, so external testing is valuable.