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Set up Steam sessions with Advanced Steam Sessions

After this guide, players host and find sessions through Steam, under their Steam name. The INVITE FRIENDS button of the lobby opens the Steam invite window, and a friend who accepts lands in your lobby.

The guide uses Advanced Sessions and Advanced Steam Sessions, two free plugins by Joshua Statzer. MPFriendslopV2 does not include them, but it already has the hooks they need: Can Invite Friends, Invite Friends and Join Invited Session on the BPI_Session interface of BP_FriendslopGameInstance.

Before you start

  • MPFriendslopV2 in Unreal Engine 5.8.
  • The Steam client, installed, running and logged in.
  • To test a join: a second PC with a second Steam account.

Download the plugins

  1. Open vreue4.com/advanced-sessions-binaries.
  2. Download AdvancedSessionsPlugin-5.8.2. It is a zip file on Google Drive.
  3. Unzip it. Inside AdvancedSessionsPlugin, you find a folder named AdvancedSessions.
  4. Close the editor.
  5. Next to MPFriendslopV2.uproject, create a folder named Plugins.
  6. Copy the AdvancedSessions folder into Plugins.

Your project now holds these two plugin folders:

MPFriendslopV2/
    MPFriendslopV2.uproject
    Plugins/
        AdvancedSessions/
            AdvancedSessions/
            AdvancedSteamSessions/

The ExampleBlueprints folder of the zip is not needed. The plugins come already built for Unreal Engine 5.8, so the editor opens without compiling anything.

Turn the plugins on

  1. Open MPFriendslopV2.
  2. Open Edit, then Plugins.
  3. Type Online Subsystem Steam in the search box, and tick its box.

The Online Subsystem Steam line in the Plugins window, ticked.

  1. Type Steam Sockets in the search box, and tick its box.

The Steam Sockets line in the Plugins window, ticked.

  1. Clear the search box. In the list on the left, click Advanced Sessions Plugin, under Project.
  2. Tick Advanced Sessions and Advanced Steam Sessions.

Advanced Sessions and Advanced Steam Sessions, both ticked.

  1. Close the editor. Do not open it again yet.

Steam Sockets carries the network driver that connects players through Steam. Since Unreal Engine 5.6, Online Subsystem Steam no longer contains one.

Tell Unreal to use Steam

  1. Open Config/DefaultEngine.ini in a text editor.

  2. Add these lines at the end of the file:

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

[OnlineSubsystem]
DefaultPlatformService=Steam

[OnlineSubsystemSteam]
bEnabled=true
SteamDevAppId=480
bInitServerOnClient=true

  3. Save the file, then open MPFriendslopV2 again.

Line Why
!NetDriverDefinitions=ClearArray Removes the network driver the engine declares by default. Unreal uses the first one it finds, so without this line it ignores the Steam driver
SteamSocketsNetDriver Players connect through Steam, to a Steam ID, with no port to open on the router
IpNetDriver The fallback. Steam does not start in Play In Editor, so the editor keeps playing over IP
DefaultPlatformService=Steam Sessions go through Steam instead of the default online subsystem
SteamDevAppId=480 Spacewar, the test app that Valve shares with every developer
bInitServerOnClient=true Lets a player host a session. Without it, HOST RUN fails

Change the parent of the game instance

  1. Open Content/MPFriendslop/Blueprints/Misc/BP_FriendslopGameInstance.
  2. Click Class Settings in the toolbar.
  3. In Details, set Parent Class to AdvancedFriendsGameInstance.

Parent Class set to Advanced Friends Game Instance.

  1. Click Compile.

AdvancedFriendsGameInstance is a child of GameInstance, so the Blueprint keeps everything it had. It adds the event that runs when a player accepts a Steam invite.

Turn the invite button on

Can Invite Friends decides whether the INVITE FRIENDS button of the lobby works. In the template it returns false, so the button shows greyed out, with STEAM NEEDS TO BE SET UP under its label.

  1. In My Blueprint, under Interfaces, double click CanInviteFriends.
  2. Add Has Online Subsystem, and type STEAM in Sub System Name.
  3. Add Is Overlay Enabled.
  4. Join both results with an AND, and connect it to Can Invite on the Return Node.

CanInviteFriends returns true when Steam runs and its overlay is available.

The button turns on by itself when the lobby opens. No widget needs to change.

Open the Steam invite window

  1. Open the Event Graph. Right click and search Event Invite Friends. Pick the one from BPI Session.
  2. Add Get Player Controller, with Player Index at 0.
  3. From the event, call Show Invite UI. Connect the player controller to its Player Controller pin.

Event Invite Friends opens the Steam invite window.

The INVITE FRIENDS button already calls Invite Friends through the interface.

Join when a friend accepts

  1. Right click in the Event Graph and search Event On Session Invite Accepted.
  2. From the event, call Join Invited Session, with Self as its Target.
  3. Connect Session to Join of the event to Session to Join of the call.

Event On Session Invite Accepted joins the session with Join Invited Session.

  1. Click Compile, then Save.

Join Invited Session is part of the template. It leaves the current session if there is one, joins the new one, then opens the lobby. Leave Auto Join Session on Accepted User Invite Received unticked in the Class Defaults, so the join happens once.

Check that it works

Steam does not start in Play In Editor. There, the game uses the default online subsystem, and INVITE FRIENDS stays greyed out.

  1. Check that Steam runs and that you are logged in.
  2. Open Content/MPFriendslop/Maps/L_MainMenu. A standalone game starts on the map open in the editor.
  3. Open the menu next to Play and pick Standalone Game.
  4. In the game, press Shift+Tab. The Steam overlay opens.
  5. Click HOST RUN, then OPEN LOBBY. The INVITE FRIENDS button is on.
  6. Click INVITE FRIENDS. The Steam window opens on your friends list.
  7. On a second PC, log in with another Steam account and launch the game.
  8. Open JOIN. Your session shows under your Steam name. Click it to join your lobby.
  9. Leave the lobby on the second PC. On the first PC, click INVITE FRIENDS and invite the second account.
  10. On the second PC, keep the game running and accept the invite. The game joins your lobby.

Before you ship your game

  • Replace 480 with the App ID that Steam gives your game.
  • A Development build writes steam_appid.txt next to the game's executable, so it starts without the Steam client launching it. A Shipping build does not. Never ship that file in your Steam depot.
  • Steam does not give the ping of a session. The session list hides it: Unknown Ping on WBP_SessionRow is 9999, the value Steam sends.

If it does not work

What you see What to check
INVITE FRIENDS stays greyed out in Play In Editor That is expected: Steam does not start in the editor. Test with Standalone Game or a packaged build.
Shift+Tab does nothing in the game Steam is not running, or you are not logged in. Also check the lines of Config/DefaultEngine.ini.
The session shows in JOIN, but a click on it brings you back to the menu with LOST CONNECTION TO THE HOST The game used the IP driver, which cannot reach a Steam ID. Check that Steam Sockets is ticked and that DriverClassName names /Script/SteamSockets.SteamSocketsNetDriver. In the log, the line AddressResolution: Result [Host=steam. ends with [FAILED]

For every setting of the Steam online subsystem, see Online Subsystem Steam in the Unreal Engine documentation.

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