> For the complete documentation index, see [llms.txt](https://docs.sfsolidsystems.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.sfsolidsystems.com/sf-steam-online-sessions/api.md). # Components / Blueprints / C++ API All multiplayer functionality is exposed via `USFOSMultiplayerSessionsSubsystem` (accessible automatically in Blueprints and C++ as a **GameInstance Subsystem**). ![SF Steam Online Sessions - Blueprint Nodes Overview](https://3719058907-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FcV1Pk81XtVqtdmLuSQlB%2Fuploads%2Fgit-blob-ef462e306bd97c2d7d40b58857273ef812999a6e%2Fsf-steam-sessions-blueprint-nodes.png?alt=media) > \[!TIP] **Interactive Graph in Sample Project:**\ > The complete, high-resolution Blueprint node graph shown above is arranged and ready to explore in the **Level Blueprint** of the **`HowToUse`** sample level (`/StraightForwardOnlineSessions/Levels/HowToUse`). You can open it in the editor to inspect all pins, connections, and copy-paste nodes directly into your own Blueprints. *** ## 📦 Data Asset: `USFSteamSessionDataAsset` A primary data asset to centralize and configure multiplayer project settings, lobby maps, gameplay levels, and predefined game modes. | Property | Type | Default | Description | | --------------------- | ------------------------------- | -------------------------------- | ---------------------------------------------------------------------------------- | | **`ProjectID`** | `FString` | `"StraightForwardMultiplayerV1"` | Unique identifier to isolate matchmaking between different projects. | | **`LobbyLevel`** | `TSoftObjectPtr` | `None` | Soft object pointer to the gathering/lobby level where sessions are created. | | **`GameplayLevels`** | `TArray` | `Empty` | List of selectable gameplay levels (with display names, thumbnails, descriptions). | | **`GameModes`** | `TArray` | `Empty` | List of predefined game modes (e.g. `"Free For All"`, `"Co-Op"`). | | **`ExtraCustomData`** | `TMap` | `Empty` | Default key-value pairs advertised to Steam. | ### Data Asset Helper Functions (BlueprintPure) * **`GetLobbyLevelPath()`**: Returns package path of the lobby level. * **`GetGameplayLevelPath(Index)`**: Returns package path of the gameplay level at specified index. * **`GetGameplayLevelNames()`**: Returns array of names for all gameplay levels (for ComboBoxes). * **`GetGameModeNames()`**: Returns array of names for all configured game modes (for ComboBoxes). * **`GetGameplayLevelEntry(Index, OutEntry)`**: Returns the level entry struct. *** ## 🧱 Structs & Configuration ### `FSFSteamSessionSettings` Clean configuration struct for creating sessions. | Property | Type | Default | Description | | ---------------- | ------------------------ | -------------------------------- | ------------------------------------------------------------------------ | | **`MaxPlayers`** | `int32` | `4` | Maximum number of allowed players in the session. | | **`MapPath`** | `FString` | `""` | Optional map URL/path to launch via ServerTravel upon creation. | | **`ProjectID`** | `FString` | `"StraightForwardMultiplayerV1"` | Unique identifier to isolate matchmaking between different projects. | | **`CustomData`** | `TMap` | `Empty` | Key-value pairs advertised to Steam (e.g. `"ServerName"`, `"GameMode"`). | *** ### `FSFSteamSearchSettings` Configuration struct for querying Steam sessions. | Property | Type | Default | Description | | ---------------------- | ------------------------ | -------------------------------- | ------------------------------------------------------------------ | | **`MaxSearchResults`** | `int32` | `20` | Maximum number of search results to return. | | **`ProjectID`** | `FString` | `"StraightForwardMultiplayerV1"` | Matches only sessions created with this Project ID. | | **`SearchFilters`** | `TMap` | `Empty` | Key-value filters to match against published session `CustomData`. | *** ## 🛠️ Main Subsystem Functions ### `CreateSessionFromDataAsset` Creates a Steam multiplayer session using the provided Data Asset configuration and travels to `LobbyLevel`. * **`SessionConfig`** *(USFSteamSessionDataAsset\*)*: The Data Asset containing map and mode definitions. * **`MaxPlayers`** *(int32, default=4)*: Player limit. * **`SelectedGameMode`** *(FString, default="Default")*: Selected game mode name (automatically saved to `CustomData["GameMode"]`). * **`SelectedGameplayLevelIndex`** *(int32, default=0)*: Selected map index from Data Asset (automatically saved to `CustomData["SelectedLevelIndex"]` and `CustomData["SelectedLevelName"]`). * **`AdditionalCustomData`** *(TMap\, advanced)*: Optional runtime key-value pairs (e.g. Server Name). ### `StartMatchFromCurrentSession` Called by the Host in the Lobby. Automatically retrieves the map selected at session creation and executes seamless `ServerTravel` (`?listen`) to transition all players to the gameplay arena. * **`SessionConfig`** *(USFSteamSessionDataAsset\*)* ### `StartMatchFromDataAsset` Allows the Host to dynamically switch and travel to any specific map index from the Data Asset. * **`SessionConfig`** *(USFSteamSessionDataAsset\*)* * **`GameplayLevelIndex`** *(int32, default=0)* ### `CreateSession` Standard function to host a session directly without Data Assets. * **`MaxPlayers`** *(int32, default=4)* * **`MapPath`** *(FString, default="")* * **`ProjectID`** *(FString, default="StraightForwardMultiplayerV1")* ### `CreateSessionWithSettings` Creates a Steam multiplayer session using the `FSFSteamSessionSettings` struct. * **`Settings`** *(FSFSteamSessionSettings)*: Session configuration. In Blueprints, can be split using **Split Struct Pin**. ### `FindSessions` Standard search for available public online sessions matching the `ProjectID`. * **`MaxSearchResults`** *(int32, default=20)* * **`ProjectID`** *(FString, default="StraightForwardMultiplayerV1")* ### `FindSessionsWithSettings` Searches for available public online sessions matching specific search settings and custom key-value filters. * **`SearchSettings`** *(FSFSteamSearchSettings)* ### `FindFriendSessions` Searches exclusively for active sessions hosted by the local player's Steam friends. ### `JoinGameSession` Connects the local player to a selected session from search results. * **`SessionResult`** *(FBlueprintSessionResult)*: The target session result. ### `ShowFriendInviteUI` Opens the native Steam Overlay friend invitation modal (1-click invitation). ### `DestroySession` Destroys the active multiplayer session and cleanly unbinds networking handles. ### `ChangeSessionLevel` Executes server travel (`?listen`) to switch maps for the server and all connected clients. * **`MapPath`** *(FString)*: Path to the target level. *** ## 🎨 Helper Functions (BlueprintPure) ### Active Local Session Helpers * **`GetCurrentSessionCustomData(Key)`**: Retrieves a metadata value (`"SelectedLevelName"`, `"GameMode"`, etc.) from the active session. Works for both Host and connected Clients in the Lobby. * **`GetAllCurrentSessionCustomData()`**: Returns all metadata key-value pairs of the active session. ### Search Result Helpers (for Server Browsers) * **`GetSessionHostName(FBlueprintSessionResult)`**: Returns the host player's Steam username. * **`GetSessionPing(FBlueprintSessionResult)`**: Returns connection ping in ms. * **`GetSessionPlayerCount(FBlueprintSessionResult, OutCurrent, OutMax)`**: Returns active and maximum player capacities. * **`GetSessionCustomData(FBlueprintSessionResult, Key)`**: Retrieves a specific custom string published by the host in `CustomData`. * **`GetAllSessionCustomData(FBlueprintSessionResult)`**: Returns the entire `TMap` of custom metadata for the session. ### Steam Profile Helpers * **`GetSteamAvatar(APlayerState* PlayerState)`**: Returns a `UTexture2D*` containing the player's Steam profile picture, cached and protected against Garbage Collection. *** ## 📢 Assignable Delegates (Async Event Callbacks) Subscribe to these event dispatchers in your Blueprints (using **Assign** or **Bind Event to...**) to respond to asynchronous Steam networking operations: | Delegate / Event | Parameters | When it Fires & Recommended Usage | | --------------------------------------- | ---------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **`OnCreateSessionCompleteEvent`** | `bool bWasSuccessful` | Fires after `CreateSession` or `CreateSessionFromDataAsset` completes. If true, the session is active and listening; if false, handle the error (e.g. notify player). | | **`OnFindSessionsCompleteEvent`** | `bool bWasSuccessful`, `TArray Results` | Fires after a public session search finishes. Pass `Results` to populate your Server Browser list widget. | | **`OnFindFriendSessionsCompleteEvent`** | `bool bWasSuccessful`, `TArray Results` | Fires after querying active lobbies hosted by Steam Friends. | | **`OnJoinSessionCompleteEvent`** | `bool bWasSuccessful` | Fires after attempting to connect via `JoinGameSession`. On success, the client automatically executes ClientTravel to the host. | | **`OnDestroySessionCompleteEvent`** | `bool bWasSuccessful` | Fires after `DestroySession` completes. Ideal place to call `Open Level` to return the player cleanly to the Main Menu. | *** ## 💡 Testing & PIE Guidelines > \[!IMPORTANT] **Steam Testing Requirement:**\ > Steam Online Subsystem features (Steam Overlay, Friend Invites, Avatars, and Matchmaking) require: > > 1. The official desktop **Steam Client** must be running and logged in on your machine. > 2. You must test via **Play > Standalone Game** (or in packaged builds). Standard PIE (Selected Viewport) runs in a non-Steam emulation environment. > 3. If testing multiplayer across 2 PCs using default `AppID 480` (Spacewar), both Steam accounts must be set to the **same Download Region** in Steam Settings (`Settings > Downloads > Download Region`).