TCP Port Checker – Check If a Port Is Open Online

TCP Port Checker

TCP Port Checker is a free online network diagnostic tool that checks whether a TCP port is reachable on a hostname or IP address.

The tool performs a real TCP connection attempt from the website server. It does not generate random or fake open-port results.

What Is a TCP Port?

A TCP port is a logical communication endpoint used by network services. Different services commonly listen on different port numbers.

For example, web servers commonly use ports 80 and 443, while other applications may use different ports.

What Does a TCP Port Checker Do?

• Checks a hostname or IP address.
• Attempts a real TCP connection.
• Measures connection response time.
• Reports whether the connection was successful.
• Reports timeout and connection errors separately.

Open vs Closed TCP Ports

If the server successfully establishes a TCP connection, the selected port is reported as reachable from our testing server.

If the connection is actively refused, the port is reported as closed or not accepting connections.

A timeout can mean that a firewall, security group, network filter or remote host is silently dropping the connection.

How to Check a TCP Port

1. Enter a hostname or IP address.
2. Enter the TCP port number.
3. Click Check TCP Port.
4. Wait for the server-side connection test.
5. Review the connection status and response time.

Common TCP Ports

Important Limitation

This tool tests connectivity from the website's server, not directly from the visitor's device. Therefore, a port can be reachable from our server while being blocked from your own network, or the opposite can occur.

For firewall troubleshooting, always consider the location of the testing server.