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Network Tools

Port Checker

Tests whether one or more TCP ports are open on a remote host. Commonly used to verify firewall rules, port forwarding, and that services like web, SSH, game or media servers are reachable.

Query

What is Port Checker?

A port checker tests whether a specific TCP port on a remote host is open and accepting connections, closed, or filtered by a firewall. Every network service — a website, a mail server, SSH, a game server — listens on a specific port, and "is the port open" is usually the very first question in diagnosing why a service isn't reachable.

This tool attempts a real TCP connection to each port you specify and reports exactly what happened, which is more reliable than guessing from a browser error message alone.

How to use the Port Checker tool

  1. 1 Enter the hostname or IP address of the server you want to check.
  2. 2 Enter one or more ports, comma-separated (e.g. 80, 443, 22) — common service ports or any custom port you're testing.
  3. 3 Run the check and read the status for each port: open, closed, or filtered/timed out.
  4. 4 If a port you expect to be open shows closed or filtered, check the server's firewall rules and, for cloud servers, the provider's security group or network ACL.

When you need this tool

  • Confirming a web server, API or database is actually reachable on the port your application expects.
  • Verifying port-forwarding rules on a home router work correctly for self-hosted services, game servers or NAS remote access.
  • Auditing which ports a server has exposed to the internet as a basic external security check.
  • Troubleshooting why a client application can't connect — ruling out "the port is closed" before debugging application-level issues.
  • Checking that a cloud provider's security group or firewall change actually took effect.

How it works

For each port you enter, the tool attempts to open a real TCP connection (a three-way handshake) to that host and port from our server. A completed handshake means the port is open; an immediate rejection (RST) means it's closed; no response at all before timeout usually means a firewall is silently dropping the connection attempt (filtered).

Frequently asked questions

What's the difference between "closed" and "filtered"?

A closed port actively rejects the connection attempt — nothing is listening there, but the host itself is reachable. A filtered (timed out) port means the connection attempt never gets a response at all, which almost always means a firewall is silently dropping the packets before they reach the host.

Why does the port show closed from here but open on my own computer?

Firewalls and router rules can allow connections from specific networks (like your home IP, if you set up a local exception) while blocking everyone else. Testing from an external server like this one tells you what the rest of the internet actually sees — which is usually what matters for a publicly hosted service.

Is checking open ports on someone else's server legal?

Checking a handful of ports on a server you don't own is generally treated like any other connection attempt a server receives daily, but full port scans against infrastructure you don't control or don't have permission to test can violate terms of service or computer-misuse laws in some jurisdictions. Only scan hosts you own or have explicit authorization to test.

Which ports should I check first for a web server?

Port 80 (HTTP) and 443 (HTTPS) for a normal website. Add 22 if you also manage the server over SSH, 21/990 for FTP, or 25/587/465 if it sends mail.