When you create a rule in Port Mapper, you need to choose an internal port, an external port, and a protocol. These values should usually match the requirements of the app, game, or server you want to make reachable.
Internal port
The internal port is the port used by the service running on your Mac.
For example, if a game server on your Mac listens on port 25565, use 25565 as the internal port.
External port
The external port is the port your router exposes to other devices or networks.
In many cases, the external port should be the same as the internal port. You can use a different external port if you know the service supports it or if you need to avoid a conflict.
TCP, UDP, or both
Different services use different network protocols. Port Mapper lets you choose TCP, UDP, or both.
- TCP: Common for web servers, remote access tools, file transfer, and many apps that require reliable connections.
- UDP: Common for some games, voice/video apps, and services where low latency is important.
- TCP + UDP: Use this when the service documentation says both protocols are required or when you are unsure and the service expects both.
How to choose the right values
- Check the documentation for the app, game, or server you are using.
- Look for a section named port forwarding, firewall, network, hosting, or server setup.
- Use the listed port number as the internal port.
- Use the same value as the external port unless the documentation says otherwise.
- Select the protocol listed in the documentation.
Avoiding conflicts
Two services usually cannot use the same external port at the same time on the same router. If a rule stays unmapped, check whether another rule, device, or router setting is already using that external port.