Plutonium

So me and a friend can't join each other our upnp is enabled for both and we tried to setup port forwarding on our router settings and when i entered the ports 4976-4977 the ingame network menu changed to say port 4978 and when i deleted the port forwarding 4976-4977 the game again changed the port 4978 back to the original 4976 and i dont know what to do anymore