Direct answer

For a Java server, an external port test checks whether an internet client can reach your listening TCP game port. It does not prove the server has correct Minecraft authentication or forwarding.

Step-by-step procedure

  1. Start the Minecraft server and confirm the log reports the listener address and port; default Java gameplay usually uses TCP 25565.
  2. Test the server from a genuinely external connection, such as a trusted friend or a phone hotspot; do not rely only on the public IP from the same LAN.
  3. If the test fails, check the host firewall, router forwarding destination, current public/WAN address and whether CGNAT is present.
  4. If TCP connects but joining fails, move to Minecraft version, online-mode, proxy forwarding and server log diagnostics.

Common mistakes and trade-offs

A closed reading while the Minecraft process is stopped is expected. Bedrock/Geyser UDP reachability requires a UDP-aware test and cannot be inferred from a TCP port checker.

How to verify it worked

Join from outside the LAN and correlate the connection attempt with the server/proxy log; a valid Minecraft handshake is stronger evidence than a generic open-port result.

Version and platform differences

When using Velocity, expose the proxy’s listener and shield Paper backends, not every server port on the network.

Official references

These sources were checked for the current MSH revision. Version-sensitive details should always be confirmed against the project documentation for the release you run.

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