Online Port Scanner
Check if specific TCP ports are open, closed, or filtered on any host.
Enter a hostname and select ports to scan
About Port Scanner
A port scanner checks whether specific TCP ports are open on a target host. Open ports indicate services listening for connections, which is useful for security audits and troubleshooting.
What we check
- TCP port connectivity status (open/closed/filtered)
- Common service identification
- Connection response time
Frequently Asked Questions
Is port scanning legal?
Port scanning your own infrastructure is legal and a common security practice. Scanning third-party systems without permission may violate laws in some jurisdictions. Always obtain authorization before scanning systems you don't own.
What's the difference between open, closed, and filtered?
Open means a service is listening and accepting connections. Closed means no service is listening but the host is reachable. Filtered means a firewall is blocking the port, so we can't determine its state.
Why are some ports commonly blocked?
Security best practices recommend closing unused ports to reduce attack surface. Firewalls often block dangerous ports (like Telnet 23) or database ports (3306, 5432) from public access.
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