I made a server (drumrd farm) and my friend can`t join to this server. When he find my map and when he click the button start, on his screen writes "No connection could be established to the multiplayer game." I don`t know what to do. We already changed the port but didn`t work.

I made a server (drumrd farm) and my friend can`t join to this server. When he find my map and when he click the button start, on his screen writes "No connection could be established to the multiplayer game." I don`t know what to do. We already changed the port but didn`t work.