Online TCP Checker

Test TCP port connectivity to any host with real-time connection results and detailed diagnostics

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7,676+

Total Calculations Run

< 15ms

Browser Execution Speed

100%

Client-Side Privacy

4.9 / 5.0

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About This Tool

The Online TCP Checker is a comprehensive tool for testing TCP port connectivity to any host on the internet or local network. Enter a hostname or IP address along with a port number, and the tool will attempt to establish a TCP connection, reporting whether the port is open, closed, or filtered. The tool provides detailed diagnostics including connection time, error messages, and protocol information. It supports both client-side WebSocket connections for immediate results and server-side fallback for environments where client-side connections are restricted. Perfect for network administrators, developers, and IT professionals troubleshooting connectivity issues.

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How to Use

Enter the target hostname or IP address in the Host field
Enter the port number to check (1-
or select from common port presets
Click 'Check TCP Connection' to initiate the test
View results showing connection status, timing, and detailed diagnostics
Use 'Check Another Port' to test additional ports on the same host

Frequently Asked Questions

Find Quick Answers

What is a TCP checker used for?

A TCP checker tests whether a specific port on a remote host is accepting TCP connections, helping diagnose network connectivity issues, verify firewall rules, and ensure services are running correctly.

Is this tool safe to use?

Yes, this tool only attempts to establish a single TCP connection to check port status. It does not perform port scanning, brute force attacks, or any malicious activities. All connections are made with user consent to specified hosts only.

Why does the connection sometimes fail?

TCP connections can fail due to firewall blocking, the port being closed, network routing issues, or the host being unreachable. The tool provides specific error messages to help identify the cause.

Can I check localhost or internal network hosts?

Yes, you can check localhost (127.0.0.1) or any internal IP address, but note that server-side checks may have limitations accessing internal networks from external servers.

What's the difference between client-side and server-side checking?

Client-side checking uses your browser's WebSocket API to make direct connections, while server-side checking uses PHP's socket functions from our server. Client-side is faster but may be blocked by browser security policies.

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