Game client/server interactions with Amazon GameLift - Amazon GameLift
Interactions diagramInteraction behaviors
Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

Game client/server interactions with Amazon GameLift

The components in your Amazon GameLift hosting solution interact with each other in specific ways to run game sessions in response to player demand. This topic describes how components communicate with each other when your game server is hosted on Amazon GameLift managed EC2 fleets, self-managed Amazon GameLift Anywhere fleets, or a hybrid solution.

Hosting solution components include a game server, the Amazon GameLift service, a client-side backend service, and a game client. The game server uses the Amazon GameLift server SDK to interact with the Amazon GameLift service. The backend service uses the Amazon GameLift service API (part of the Amazon SDK) to interact with the service on behalf of the game client. When joining a game session, the game client connects directly to a game session using the game session's unique IP address and port number.

Interactions diagram

The following diagram illustrates how your game hosting components interact so that the Amazon GameLift service can track the status of game server availability and start game sessions in response to player demands.

Game client/server behavior for the key interactions, as described in this topic.

Interaction behaviors

The following sections describe the sequence of events in each of the key interactions.

Initializing a game server process

On startup, a game server process establishes communication with the Amazon GameLift service and reports its status as ready to host a game session.

  1. A new process of the game server executable starts running on a hosting resource.

  2. The game server process calls the following server SDK operations in sequence:

    1. InitSDK() to initialize the server SDK, authenticate the server process, and establish communication with the Amazon GameLift service.

    2. ProcessReady() to communicate readiness to host a game session. This call also reports the process's connection information, which game clients use to connect to the game session, and other information.

    The server process then waits for prompts from the Amazon GameLift service.

  3. Amazon GameLift updates the status of the server process to ACTIVE and available to host a new game session.

  4. Amazon GameLift begins periodically calling the onHealthCheck callback to request a health status from the server processes. These calls continue while the server process remains in active status. The server process must respond healthy or not healthy within one minute. If the server process responds not healthy or doesn't respond, at some point the Amazon GameLift service changes the server process's active status and stops sending requests to start game session.

Creating a game session

The Amazon GameLift service starts a new game session in response to a request from a player to play the game.

  1. A player using the game client asks to join a game session. Depending on how your game handles the player join process, the game client sends a request to the backend service.

  2. If the player join process requires starting a new game session, the backend service sends a request for a new game session to the Amazon GameLift service. This request calls the service API operation StartGameSessionPlacement(). (As an alternative, the backend service might call StartMatchmaking(), or CreateGameSession().)

  3. The Amazon GameLift service responds by creating a new GameSessionPlacement ticket with status PENDING. It returns ticket information to the backend service, so that it can track the placement ticket status and determine when the game session is ready for players. For more information, see Set up event notification for game session placement.

  4. The Amazon GameLift service starts the game session placement process. It identifies which fleets to look at and searches those fleets for an active server process that's not hosting a game session. On locating an available server process, the Amazon GameLift service does the following:

    1. Creates a GameSession object with the game session settings and player data from the placement request, and sets the status to ACTIVATING.

    2. Prompts the server process to start a game session. The service invokes the server process's onStartGameSession callback and passes the GameSession object.

    3. Changes the server process's number of game sessions to 1.

  5. The server process runs its onStartGameSession callback function. When the server process is ready to accept player connections, it calls the server SDK operation ActivateGameSession() and waits for player connections.

  6. The Amazon GameLift service updates the GameSession object with connection information for the server process (as reported in the call to ProcessReady()) and sets the game session status to ACTIVE. It also updates the GameSessionPlacement ticket status to FULFILLED.

  7. The backend service calls DescribeGameSessionPlacement() to check ticket status and get game session information. When the game session is active, the backend service notifies the game client and passes the game session connection information.

  8. The game client uses the connection information to connect directly to the game server process and join the game session.

Adding a player to a game

A game can optionally use player sessions to track player connections to game sessions. Player sessions can be created individually or as part of a game session placement request.

  1. The backend service calls the service API operation CreatePlayerSession() with a game session ID.

  2. The Amazon GameLift service checks the game session status (must be ACTIVE), and looks for an open player slot in the game session. If a slot is available, then the service does the following:

    1. Creates a new PlayerSession object and sets the status to RESERVED.

    2. Responds to the backend service request with player session information.

  3. The backend service passes player session information to the game client along with game session connection information.

  4. The game client uses the connection information and player session ID to connect directly to the game server process and ask to join the game session.

  5. In response to a game client join attempt, the game server process calls the service API operation AcceptPlayerSession() to validate the player session ID. The server process either accepts or rejects the connection.

  6. The Amazon GameLift service does one of the following:

    1. If the connection is accepted, then Amazon GameLift sets the PlayerSession status to ACTIVE and passes the PlayerSession to the game server process.

    2. If the game server process doesn't call AcceptPlayerSession() for the player session ID within a certain time period after the original CreatePlayerSession() request, the Amazon GameLift service changes the PlayerSession status to TIMEDOUT and reopens the player slot in the game session.

Removing a player

For games that use player sessions, the game server process notifies the Amazon GameLift service when a player disconnects. The service uses this information to track the status of player slots in a game session and can allow new players to use open slots.

  1. A player disconnects from the game session.

  2. The game server process detects the lost connection and calls the server SDK operation RemovePlayerSession().

  3. The Amazon GameLift service changes the player session status to COMPLETED and reopens the player slot in the game session.

Shutting down the game session

At the end of a game session, or when shutting down the game session, the server process notifies the Amazon GameLift service of game session status.

  1. The game server process ends the game session and initiates process shut down by calling the server SDK operation ProcessEnding().

  2. The Amazon GameLift service does the following:

    1. Uploads game session logs to Amazon Simple Storage Service (Amazon S3).

    2. Changes the game session status to TERMINATED.

    3. Changes the server process status to TERMINATED.

    4. Depending on how the hosting solution is designed, the newly available hosting resources are allocated to run a new game server process.