after re-reading your description a few times - i think there’s a basic misunderstanding of http and dedicated server connections.
when you are trying to connect to a dedicated server (i.e. the project.exe file) – this is NOT accessible as:
open http://serverip:port/
the UE4 (game) network is not HTTP.
but, rather - you connect to the dedicated server with:
open serverip:port
now, it sounds like you got the websocket netdriver for UE4 working.
that said, to play on your thirdparty dedicated server you would need to ensure you are connected to the external IP address:port – so, if your dedicated server is publicly accessible, excellent! all you need is:
open serverip
but, if it is behind a port forwarding box, find out where your game’s port number is forwarded to and then open your connection to that value.
open serverip:port
please see the following pages for more details: