Plutonium

Resxt it didn't worked, thats why i was posting here

So, I've downloaded Plutonium and tried to join a friend, but I can't. When I try to join him through the 'Friends' menu, it says he is in a private game. When I try to join him using the command 'connect,' it doesn't work either.

I followed the guide and activated UPnP, but it didn't work either.

The only way I can play with him is when we both join the same public server.

Does anyone know how to fix this?