How to check if Minecraft Java TCP port is open?

Distinguish between three separate results when testing the Java port. There may be a process listening on the port, TCP may be accessible from the outside, and the Minecraft protocol may respond.

Step by step

1. Find the port you configured in the ss -ltn output on the Linux server. If listening is only on 127.0.0.1 it cannot be accessed directly from the outside network.

2. Run Test-NetConnection play.example.net -Port 25565 on a Windows device on another network. If you are using a private port, write it in the command.

3. If the TCP test fails, examine the server binding address, provider security rules, and modem routing. If TCP passes and Minecraft doesn't respond, check the service or proxy configuration on the target.

4. Do the last test with the real Java client. It is normal for the TCP test to be successful if another service is listening on the port.

Keep in mind

This command does not replace the Bedrock UDP test.

Source and tools

• Microsoft Learn: Test-NetConnection
• Diagnose Minecraft connection