Port Checker

TCP check

Check whether a TCP port is open, closed, or filtered on any hostname or IP address.

Last updated June 8, 2026

Enter a host and port, then run the check.

About Port Checker

A port checker sends a TCP connection attempt to a specific port on a remote host and reports whether the connection succeeded, was refused, or timed out — telling you whether the port is open, closed, or filtered by a firewall. This is the fastest way to verify firewall rules, confirm that a service is actually listening on the expected port after a deployment, or diagnose why a remote service is unreachable. Open means a service responded and accepted the connection. Closed means the host responded but nothing is listening on that port — the OS sent a TCP RST. Filtered means the connection attempt timed out without any response — a firewall is silently blocking the packets. Our free port checker runs the TCP test from our server, so results reflect public internet reachability rather than your local network. The tool supports any hostname or IP address and any port from 1 to 65535. Private and loopback addresses (10.x, 192.168.x, 172.16–31.x, 127.x) are blocked to prevent misuse. Common service ports — HTTP (80), HTTPS (443), SSH (22), FTP (21), MySQL (3306), SMTP (25 and 587), and HTTP-alt (8080) — are available as quick-select buttons.

Common use cases

Verify that a firewall rule change took effect and the correct ports are now open.
Confirm that a web server, database, or SSH daemon is listening after a deployment.
Diagnose why a remote service (API, database, mail server) is unreachable.
Test port accessibility before configuring a VPN or tunnel endpoint.
Check whether a cloud instance security group allows the intended traffic.

How to use this tool

Enter the hostname (for example, example.com) or IP address you want to check.
Type a port number between 1 and 65535, or click one of the common port quick-select buttons.
Click "Check port" to run a live TCP connection test from our server.
Review the result showing whether the port is open, closed, or filtered, along with the resolved IP and response time.

Frequently asked questions

What does "filtered" mean?

Filtered means the connection attempt timed out without receiving any response. A firewall or network device is silently dropping the packets rather than rejecting them. It differs from "closed", where the host responds immediately with a TCP RST to say nothing is listening.

Why is my port showing as closed when my service is running?

The service may be binding to a specific interface (127.0.0.1 only) instead of all interfaces (0.0.0.0). It could also be blocked by a host firewall (iptables, Windows Firewall, ufw) that operates below the application layer. Check that the service binds to 0.0.0.0 and that the local firewall allows the port.

Where does the port check originate from?

The TCP test is performed from our server. If your target host has geo-IP filtering or allowlists specific IP ranges, the result may differ from what users in other regions see.

Is this the same as a port scan?

No. A port scan checks many ports at once to map a host's attack surface. This tool checks a single port at a time, which is the standard diagnostic check used by developers and sysadmins to verify a known service is reachable.

Can I check ports on private IP addresses?

No. Private and loopback IP ranges (10.x, 192.168.x, 172.16–31.x, 127.x) are blocked to prevent the tool from being used to probe internal networks.

Look up PTR hostnames from IPv4 addresses.

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