A lobby is a group of players. Read Setting Up Matchmaking to see how lobbies and queues fit together. Call InitializeSimpl first. See Setup.

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Calls

In C++, every call is a method on USimplClientSubsystem. Each one takes an optional last argument: a function that runs when the call is done. Blueprints get the same calls as nodes. See Blueprints. “Host only” means only the lobby’s host can do it. Other players get the error NOT_HOST. The queue and match calls are on Queues and matches.

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Player state

Player state is a small set of values you send when you create or join a lobby. Queue rules read it. In C++ it is a TMap<FString, FSimplStateValue>. A value can be a string, a number, a bool, a list of strings, a list of numbers, or JSON text. Numbers are 32-bit floats. Keep IDs as strings. UpdatePlayerState takes the new state and a bMerge flag. It is on by default, so the new values are added to your old ones. Other players do not get an event when your state changes. They see it the next time their lobby is read. Team and role are set by the queue. Only members of the lobby can see them.

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Browse lobbies

BrowseLobbies takes a queue ID, a status, a region, a limit, an offset and a sort. The plugin only sends the ones you fill in.
  • Limit is at most 100.
  • Sort can be created_at_desc, created_at_asc or player_count_desc.
  • The answer has the lobbies, a Total and a bHasMore flag.
Do not browse on a timer. See Rate limits.

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What the plugin does for you

  • One lobby at a time. Creating, joining or reconnecting leaves the current lobby first. OnLobbyLeft fires for that.
  • Version tag. It adds version_tag to your state if you did not.
  • Joining a lobby you are already in. JoinLobby reconnects you instead of failing.
  • Keeping the lobby fresh. It listens for live events and also reads the lobby on a timer. See Events.
  • Retries. It retries TRY_AGAIN. See Errors.

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What you must save yourself

The plugin keeps the lobby ID in memory only. GetLastLobbyId returns it. If you want to reconnect after your game restarts, save the lobby ID and the player ID yourself. After the restart, call InitializeSimpl with the same player ID, then ReconnectToLobby with the saved lobby ID.