Port Checker — Test Open and Closed Ports Online
Last Updated: April 2026
Test if any TCP port is open or closed on any host or IP address. Free online port checker for developers and network admins. No software required. Instant results.
Use Port Checker
Launch the Port Checker tool — fully free, no signup required.
What Is a Network Port?
Common Port Numbers Reference
| Port | Protocol | Common Use |
|---|---|---|
| 21 | FTP | File transfer |
| 22 | SSH | Secure remote access |
| 25 | SMTP | Email sending |
| 53 | DNS | Domain name resolution |
| 80 | HTTP | Web traffic |
| 110 | POP3 | Email retrieval |
| 143 | IMAP | Email access |
| 443 | HTTPS | Secure web traffic |
| 3306 | MySQL | Database connections |
| 3389 | RDP | Remote desktop |
| 8080 | HTTP Alt | Web development |
| 27017 | MongoDB | Database connections |
How to Use the Port Checker
Why Is My Port Closed?
Frequently Asked Questions
Q: What is a port checker?
A: A port checker tests whether a specific port on a server or computer is open (accepting connections) or closed (blocking connections). It is used by network administrators and developers to troubleshoot firewall and connectivity issues.
Q: Why is my port showing as closed?
A: A port may appear closed because of a firewall rule blocking it, the service using that port is not running, or the router has not forwarded the port correctly.
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