# Integrate Amazon GameLift Servers with a Unity game server project
<a name="integration-unity-server-sdk4"></a>

**Note**  
This topic provides information for an earlier version of the Amazon GameLift Servers plugin for Unity. Version 1.x uses the server SDK for Amazon GameLift Servers 4.x or earlier. For documentation on the latest plugin version, which uses server SDK 5.x and supports newer features such as Amazon GameLift Servers Anywhere and managed container hosting, see [Amazon GameLift Servers plugin for Unity (server SDK 5.x)](unity-plug-in.md).

This topic helps you prepare your custom game server for hosting on Amazon GameLift Servers. The game server must be able to notify Amazon GameLift Servers about its status, to start and stop game sessions when prompted, and to perform other tasks. For more information, see  [Add Amazon GameLift Servers to your game server with the server SDK](gamelift-sdk-server-api.md).

## Prerequisites
<a name="integration-unity-server-sdk4-prereq"></a>

Before integrating your game server, complete the following tasks: 
+ [Set up an IAM service role for Amazon GameLift Servers](setting-up-role.md)
+ [Install and set up the plugin](unity-plug-in-sdk4.md#unity-plug-in-sdk4-install)

## Set up a new server process
<a name="integration-unity-server-sdk4-server-process"></a>

**Note**  
This topic refers to Amazon GameLift Servers plugin for Unity version 1.0.0, which uses server SDK 4.x or earlier.

Set up communication with Amazon GameLift Servers and report that the server process is ready to host a game session. 

1. Initialize the server SDK by calling `InitSDK()`. 

1. To prepare the server to accept a game session, call `ProcessReady()` with the connection port and game session location details. Include the names of callback functions that Amazon GameLift Servers service invokes, such as `OnGameSession()`, `OnGameSessionUpdate()`, `OnProcessTerminate()`, `OnHealthCheck()`. Amazon GameLift Servers might take a few minutes to provide a callback.

1. Amazon GameLift Servers updates the status of the server process to `ACTIVE`.

1. Amazon GameLift Servers calls `onHealthCheck` periodically.

The following code example shows how to set up a simple server process with Amazon GameLift Servers. 

```
//initSDK
var initSDKOutcome = GameLiftServerAPI.InitSDK();
           
//processReady
// Set parameters and call ProcessReady
var processParams = new ProcessParameters(
    this.OnGameSession,
    this.OnProcessTerminate,
    this.OnHealthCheck,
    this.OnGameSessionUpdate,
    port,
    // Examples of log and error files written by the game server
    new LogParameters(new List<string>()          
        {
            "C:\\game\\logs",
            "C:\\game\\error"
        })
);
               
var processReadyOutcome = GameLiftServerAPI.ProcessReady(processParams);
               
// Implement callback functions
void OnGameSession(GameSession gameSession)
{
    // game-specific tasks when starting a new game session, such as loading map
    // When ready to receive players
    var activateGameSessionOutcome = GameLiftServerAPI.ActivateGameSession();
}
               
void OnProcessTerminate()
{
    // game-specific tasks required to gracefully shut down a game session, 
    // such as notifying players, preserving game state data, and other cleanup
    var ProcessEndingOutcome = GameLiftServerAPI.ProcessEnding();
}
               
bool OnHealthCheck()
{
    bool isHealthy;
    // complete health evaluation within 60 seconds and set health
    return isHealthy;
}
```

## Start a game session
<a name="integration-unity-server-sdk4-start-game-session"></a>

**Note**  
This topic refers to Amazon GameLift Servers plugin for Unity version 1.0.0, which uses server SDK 4.x or earlier.

After game initialization is complete, you can start a game session.

1. Implement the callback function `onStartGameSession`. Amazon GameLift Servers invokes this method to start a new game session on the server process and receive player connections.

1. To activate a game session, call `ActivateGameSession()`. For more information about the SDK, see [C\$1 server SDK for Amazon GameLift Servers 4.x -- Actions](integration-server-sdk-csharp-ref-actions.md).

The following code example illustrates how to start a game session with Amazon GameLift Servers. 

```
void OnStartGameSession(GameSession gameSession)
{
    // game-specific tasks when starting a new game session, such as loading map   
    ...
    // When ready to receive players   
    var activateGameSessionOutcome = GameLiftServerAPI.ActivateGameSession();
}
```

## End a game session
<a name="integration-unity-server-sdk4-end-game-session"></a>

**Note**  
This topic refers to Amazon GameLift Servers plugin for Unity version 1.0.0, which uses server SDK 4.x or earlier.

Notify Amazon GameLift Servers when a game session is ending. As a best practice, shut down server processes after game sessions complete to recycle and refresh hosting resources. 

1. Set up a function named `onProcessTerminate` to receive requests from Amazon GameLift Servers and call `ProcessEnding()`. 

1. The process status changes to `TERMINATED`.

The following example describes how to end a process for a game session.

```
var processEndingOutcome = GameLiftServerAPI.ProcessEnding();

if (processReadyOutcome.Success)
   Environment.Exit(0);

// otherwise, exit with error code
Environment.Exit(errorCode);
```

## Create server build and upload to Amazon GameLift Servers
<a name="integration-unity-server-sdk4-gamelift-connection"></a>

**Note**  
This topic refers to Amazon GameLift Servers plugin for Unity version 1.0.0, which uses server SDK 4.x or earlier.

After you integrate your game server with Amazon GameLift Servers, upload the build files to a fleet so that Amazon GameLift Servers can deploy it for game hosting. For more information on how to upload your server to Amazon GameLift Servers, see [Create a game server build for Amazon GameLift Servers](gamelift-build-cli-uploading.md).