Multiplayer #

Pragma Engine Multiplayer services manage the workflow for grouping players into parties, matching parties, and getting into a game. A successful game flow consists of several stages, from partying up to playing a game to completing a game instance. While ideally players will consistently travel through a preset flow, Multiplayer services must not only build out a success path, but must also account for potential issues caused by external services such as game server providers and ISPs. In this section, we’ll take a look at the pieces that make up Multiplayer services and explain how to customize and leverage the various features.

Multiplayer flow overview #

The following graphic and numbered list present a simplified overview of how Pragma Engine facilitates Multiplayer services. Items in blue represent Pragma services.

1. Players create parties and make selections.

   Using the Party service, players can create a party and invite other players to join; solo players are parties of one. Within the party, players can coordinate with each other and make pregame party and player-specific selections.

2. Parties enter matchmaking and are matched with opponents.

   When players are ready, a party leader can enter the party into matchmaking. The Matchmaking service uses custom logic to compare parties to form appropriate matches to send to the game server.

3. Game server is allocated.

   Once matches are formed, the Matchmaking service creates a New Game Instance. Your fleet management solution (such as the Pragma-provided Fleet service) should keep track of game server capacity and the number of game instances allocated. The fleet manager is responsible for finding an available game server or provisioning an additional server if everything is at capacity.

4. Connection details are sent and game instance starts.

   The chosen game server communicates with the Game Instance service to get game details. The Game Instance service sends connection information back to involved players, who connect to the waiting server. Once all players connect, the game instance starts.

5. Game instance end data is processed.

   When the game instance ends, the game server communicates results to the Game Instance service, which processes and logs this data (such as item granting and player stats tracking).

6. Game instance end updates are sent.

   The Game Instance service sends a notification to players with game instance results. Players remain in their existing parties.

Multiplayer components #

Let’s take a look at the various components that must work together for a successful game flow.

Player client #

This is the software running on a player’s machine, which is how a player experiences a game. The player client is responsible for everything the player sees, and for sending and receiving data from your game service, which consists of Pragma Engine, your game server, and any other in-house or third party services you might be using.

Pragma provides the Game Loop API for Unreal and Unity so that your player client can communicate with Pragma Engine. To interact with the Unreal Game Loop API, you must first call the Initialize() function:

Player->GameLoopApi().Initialize();

Pragma Engine services #

The engine has several services and plugins working in concert to get players matched up and playing.

Some of these behaviors can be customized or extended through various custom plugins.

Pragma Engine multiplayer plugins #

Game server #

Studios are responsible for authoring the game server, which hosts the software responsible for everything a player sees and does while involved in a game instance. The game server is expected to repeatedly report its capacity for hosting game instances to the Pragma Engine backend, and will receive game instances to start via this polling flow. The game server is then expected to report when the game instance is ready. The Pragma Match API (for Unreal and Unity) provides functionality to assist with making these calls.

To integrate with the Pragma Engine Multiplayer services, a game server will need to interact with the Pragma SDK via WebSockets or HTTP web protocol. Pragma recommends you use Websockets, which the Pragma Match API uses by default. Note that WebSocket connections are required adding parties to active game instances.

To use HTTP instead, override the SDK config and set the partnerProtocolType to HTTP, as shown in the following examples. A valid HTTP use case would be to support websites interacting with Partner endpoints.

const auto* Subsystem = GetLocalPlayer()->GetSubsystem<UPragmaLocalPlayerSubsystem>();
auto Runtime = Subsystem->Runtime();
Runtime->Config().BackendAddress = "http://127.0.0.1:10000";
Runtime->Config().PartnerProtocolType = EPragmaProtocolType::Http;
auto Server = Runtime->Server();
Server->Connect(FServer::FConnectedDelegate::CreateLambda([this]
{
    // OnComplete delegate
}));

PragmaSessionManager.SetConfig(new SdkConfig.Data
{
    partnerBackendAddress = _gameConfig.PragmaBackendAddress,
    partnerSessionGameAuthToken = _gameConfig.PartnerGameToken,
    partnerSessionSocialAuthToken = _gameConfig.PartnerSocialToken,
    partnerProtocolType = ProtocolType.Http
   
});
var connectPromise = new Promise();
_session.Connect(connectPromise.Complete);
yield return connectPromise.Future;
if (connectPromise.Future.Result.IsFailure)
{
    db.Error(
      LogTag, "Failed to initialize Server: {0}", connectPromise.Future.Result.ErrorCode
    );
}

To learn about player client/game server version compatibility, see Manage game server compatibility.

Topics in this section #