I struggled getting the server/client to connect in UE 5.1 until I went through all the various options people recommended (mainly it was adding ?listen to a server that was preventing it from working correctly, so don’t do that).
For me the final commands were:
Server:
<EDITOR> <UPROJECT> /Game/ThirdPerson/Maps/ThirdPersonMap -server -log
Client
<EDITOR> <UPROJECT> 127.0.0.1:7779 -game -log
Port might depend on what your UE defaults to, but the localhost IP 127.0.0.1 should work for LAN.
Lastly, I’m not sure how often we’ll be launching this way throughout the course but I couldn’t resist spending a bunch of time making a very simple bat file to launch UE for me as Standalone, Server, Host, or Client, that you can get here:
Save it in a text file and change the extension to .bat and you should be good to go. I’m not a bat wizard, but it’s pretty straightforward and should be easy to change the path variables to reflect your particular setup.