RIght now I’m using Advanced Steam Sessions and heavily modified it so I can get the functionality that I want. Right now I want the player to be able to invite friends using the Steam Shift-Tab menu / Game overlay and it works fine but only when I use the AdvancedSessions/AdvancedFriendLibrary/ShowInviteUI which is linked with the online subsystem function IOnlineExternalUI::ShowInviteUI().
Steam has its own function to allow friends to join you: bool SetRichPresence( const char *pchKey, const char *pchValue ); [STEAM API]. You can set the RichPresense and enable steam to show your player ‘in game’, then your friends can join the lobby but it needs a few things.
First steam needs a command for how it should connect to the server.
TLDR: How do I get the IP Address of a Session from OnlineSubsystem and use it in Steamworks to let friends join each other?