I tried creating subclasses of PartyBeconHost and PartyBeaconClient. I create and initialize the host beacon on the server and it seems fine, while on the client after creating the client beacon I call RequestReservation and I get this:
[2016.12.07-15.06.19:972][858]LogNet: CreateNamedNetDriver failed to create driver from definition BeaconNetDriver
[2016.12.07-15.06.19:973][858]LogBeacon:Warning: RequestReservation: Failure to init client beacon with steam.76561198050836541:15000//Game/Maps/MainMenuLevel.
I added some beacon related lines to DefaultEngine.ini as suggested here AOnlineBeaconHost and BeaconNetDriver problem - C++ - Unreal Engine Forums
but I still get the same error. Any idea?