E2160 - EarthNet Ports
Earth 2160 requires the following game ports to be open and forwarded to your PC, if they are not then you will not be able to connect to or host multiplayer games.
UDP: 17771-17772, 17172, 6073 and 2300-2400
You can use the following guides if you're unsure how to forward ports on your router to your PC: PortForward
Also ensure you have the network settings configured as below: