I copied the ini file from the tutorial for the DefaultEngine. I have tried using both
[OnlineSubsystem]
DefaultPlatformService=Steam and DefaultPlatformService=Null (I thought this was what was needed for LAN).
I am running the same project from my laptop and hosting a game and joining on my computer and vice versa. They are the exact same version of the project which was how it was shown in the video.
From 4.13 there is a new place where is should be set to Steam, in the Engine click Edit/Plugins/Online Platform/Online Subsystem Steam. Check this in, and restart the engine, maybe this will fix it. The tutorial was made pre 4.13, that’s why this step is not included in there.
If it is failing to join a session, it could be a couple things.
How are you hosting the session? As in, are you hosting and joining the game on the same computer with two windows? Or, are you running the game on two computers?
If you are trying to host/join via Steam, yeah, this would prevent you from doing so. Steam doesn’t like to handle two connections with one computer / Steam account.
However, if you are not using Steam, you should be able to run two clients (host/client) on the same machine.