NetCheck Tools

Open Port Checker

Verify from the outside which ports on your server are actually reachable. Ideal for testing firewall rules, cloud security groups and router port forwarding.

Why check from the outside?

Running netstat or ss on the server tells you what is listening — not what is reachable. Between your service and the internet sit the OS firewall, cloud security groups, network ACLs and sometimes a NAT router. This checker connects from the public internet, so it validates the entire chain at once.

A quick exposure audit

  1. Test the ports you expect open (80, 443): they should be “open”
  2. Test the ports that must stay private (3306, 5432, 6379, 27017): they should be “timeout” or “closed”
  3. Test SSH (22): ideally restricted by source IP, so “timeout” from here can be a good sign

If a should-be-open port times out, work through our step-by-step port troubleshooting guide.

Frequently asked questions

›How do I check if a port is open on my server?

Enter your server's public hostname or IP and the port number, then run the check. The tool attempts a real TCP connection from the internet: “open” confirms your firewall and service are configured correctly for external access.

›Which ports should be open on a typical web server?

Usually only 80 (HTTP), 443 (HTTPS) and a firewalled/port-restricted SSH (22). Everything else — databases, Redis, admin panels, monitoring agents — should be closed to the public and reached over VPN or private networking.

›Is having open ports dangerous?

An open port is only as safe as the service behind it. Exposed databases and remote-desktop ports are among the most attacked things on the internet. Audit your open ports regularly and close anything that doesn't strictly need public access.

›Does this tool work for checking port forwarding on my router?

Yes — that is one of its most common uses. Set up the forwarding rule, then test your public IP with the forwarded port. If the result is “timeout”, the rule isn't working or your ISP blocks the port (common for 25, 137-139 and 445).

Related tools

Port Checker

The core TCP port test with latency measurement.

Check If a Port Is Open

Troubleshooting steps when a port won't open.

DNS Lookup

Make sure your hostname points at the right server.