There are people who have achieved the functionality which you are trying to create through a dedicated server of their own, generally they have used AWS for this as its quite extensible. But then you can also host your own server on your static IP and try connecting it to the client.
Also steam works also gives free server for testing it seems, you can use them as well.
OR else use some free cloud hosting server, host your UE4 server there and connect to it.