Fatal Error when trying to find Steam lobbies through C++ in Unreal 5.5/5.6.

Development Programming & Scripting
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1

Hi, I’ve been having an issue with finding sessions in Unreal 5.5/5.6. In a packaged build when testing multiplayer through 2 different Steam accounts on 2 different computers, I always get a fatal error when I attempt to Find Sessions. I’ve tried a bunch of different combinations of settings and I simply cannot get it to work.

My session create code looks like this:

FOnlineSessionSettings Settings;
Settings.bAllowJoinInProgress = true;
Settings.bIsDedicated = false;
Settings.bShouldAdvertise = true;
Settings.bUsesPresence = true;
Settings.NumPublicConnections = 5;
Settings.bUseLobbiesIfAvailable = true;
	
SessionInterface->CreateSession(0, NAME_GameSession, Settings);

And my find sessions code looks like this:

SessionSearch = MakeShared<FOnlineSessionSearch>();
SessionSearch->bIsLanQuery = false;
SessionSearch->MaxSearchResults = 10000;
SessionSearch->QuerySettings.Set(SEARCH_LOBBIES, true, EOnlineComparisonOp::Equals);
SessionInterface->FindSessions(0, SessionSearch.ToSharedRef());

DefaultEngine.ini:

[/Script/Engine.GameEngine]
!NetDriverDefinitions=ClearArray
+NetDriverDefinitions=(DefName="GameNetDriver",DriverClassName="/Script/SteamSockets.SteamSocketsNetDriver",DriverClassNameFallback="OnlineSubsystemUtils.IpNetDriver")

[OnlineSubsystem]
DefaultPlatformService=Steam

[OnlineSubsystemSteam]
bEnabled=True
SteamDevAppId=[My id]
bInitServerOnClient=true
SteamAppId=[My id]

[/Script/OnlineSubsystemUtils.IpNetDriver]
MaxClientRate=1000000000
MaxInternetClientRate=1000000000
InitialConnectTimeout=120.0

[/Script/OnlineSubsystemSteam.SteamNetDriver]
NetConnectionClassName=OnlineSubsystemSteam.SteamNetConnection

Build.cs file:

PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;
	
		PublicDependencyModuleNames.AddRange(new string[]
		{
			"Core",
			"CoreOnline",
			"CoreUObject",
			"GameplayAbilities",
			"GameplayTags",
			"GameplayTasks",
			"Engine",
			"EnhancedInput",
			"InputCore",
			"Networking",
			"OnlineSubsystem",
			"OnlineSubsystemUtils",
			"Paper2D",
			"UMG"
		});

		PrivateDependencyModuleNames.AddRange(new string[]
		{
			"EnhancedInput",
			"OnlineSubsystemSteam"
		});

If I remove the line SessionSearch->QuerySettings.Set(SEARCH_LOBBIES, true, EOnlineComparisonOp::Equals); it won’t crash with a fatal error anymore but I also won’t find any sessions at all. There also seems to be no difference whether I use SEARCH_LOBBIES or SEARCH_PRESENCE, it will crash just in the same way.

I also tried both the SteamSockets net driver and the default Steam Net Driver, same issue. Another thing I noticed while debugging is that if I don’t bind anything to the OnFindSessionsCompleteDelegates, it also won’t crash so I thought it could perhaps be a object lifetime issue or similar, but the problem is that it crashes way before it even attampts to broadcast the delegate, so I’m a bit dumbfounded as to what the issue might be.

I would be thankful if anyone can help me solve this issue, as I’ve been stuck on it quite some time.

2

I’m bumping this, as it’s very crucial for me to get this fixed.

3

It’s been 7 months and I have been focusing on other things but I have to get this bumped again as it’s still not working.

An update to this though is that if I start the actual gameplay map as the host and send an invite through Steam that the other player accepts, the other player will correctly enter the session. However, if I send an invite through Steam as the host when in the menu, the other player can join through the invite and arrives at the menu, but if I do a ServerTravel to the gameplay map the host will crash with a Fatal Error as well.