# Migrate to server SDK 5.x for Amazon GameLift Servers
<a name="reference-serversdk5-migration"></a>

To update a game project to use server SDK version 5.x, make the following changes:

**Note**  
If you need to continue using server SDK version 4.x or earlier, see [Server SDK for Amazon GameLift Servers version 4 and earlier](reference-serversdk4.md) for documentation and download information. For SDK version 4.0.2 specifically, you can download it from the [official GitHub releases](https://github.com/amazon-gamelift/amazon-gamelift-servers-csharp-server-sdk/releases).

1. Get the latest server SDK for Amazon GameLift Servers package for your development environment **[[Download site](https://aws.amazon.com/gamelift/servers/getting-started-sdks/)]**. Follow the installation instructions in the `Readme` file for your downloaded package and version. See these instructions for using the server SDKs with your game project.
   + [For development environments using C\$1\$1, C\$1, or Go](gamelift-sdk-server-api.md)
   + [For Unreal Engine projects (C\$1\$1 server SDK for Unreal libraries only)](integration-engines-setup-unreal.md)
   + [For Unity projects (C\$1 server SDK for Unity libraries only)](integration-engines-unity-using.md)
   + [For use with the Amazon GameLift Servers plugin for Unreal Engine](unreal-plugin.md)
   + [For use with the Amazon GameLift Servers plugin for Unity](unity-plug-in.md)

1. Update your server code as follows:
   + Change the server code callback function `onCreateGameSession()` to `onStartGameSession()`.
   + Update the `InitSDK()` inputs as appropriate: 
     + If you plan to deploy the game server build to either an Amazon GameLift Servers managed EC2 fleet or an Anywhere fleet with the Amazon GameLift Servers Agent: 

       Call `InitSDK()` with no parameters ([C\$1\$1](integration-server-sdk5-cpp-actions.md#integration-server-sdk5-cpp-initsdk)) ([C\$1](integration-server-sdk5-csharp-actions.md#integration-server-sdk5-csharp-initsdk)) ([Unreal](integration-server-sdk5-unreal-actions.md#integration-server-sdk5-unreal-initsdk)). This call sets up the compute environment and a WebSocket connection to the Amazon GameLift Servers service. 
     + If you plan to deploy the game server build to an Anywhere fleet without the Amazon GameLift Servers Agent:

       Call `InitSDK()` with server parameters ([C\$1\$1](integration-server-sdk5-cpp-actions.md#integration-server-sdk5-cpp-initsdk-anywhere)) ([C\$1](integration-server-sdk5-csharp-actions.md#integration-server-sdk5-csharp-initsdk-anywhere)) ([Unreal](integration-server-sdk5-unreal-actions.md#integration-server-sdk5-unreal-initsdk-anywhere)). A game server process uses these parameters to establish a connection with the Amazon GameLift Servers service.

1. If your game server build or other hosted applications communicate with other AWS resources while running, you'll need to change how the application gets access to those resources. Replace the use of `AssumeRoleCredentials` with the new server SDK action `GetFleetRoleCredentials()` (for game servers) or use shared credentials (for other applications). For more on how to implement this change, see [Connect your Amazon GameLift Servers hosted game server to other AWS resources](gamelift-sdk-server-resources.md).

1. If your project called the server SDK action `GetInstanceCertificate()` to retrieve a TLS certificate, modify your code to use the new `GetComputeCertificate()` ([C\$1\$1](integration-server-sdk5-cpp-actions.md#integration-server-sdk5-cpp-getcomputecertificate)) ([C\$1](integration-server-sdk5-csharp-actions.md#integration-server-sdk5-csharp-getcomputecertificate)) ([Unreal](integration-server-sdk5-unreal-actions.md#integration-server-sdk5-unreal-getcomputecertificate)) instead.

1. When uploading your game build to Amazon GameLift Servers (such as with [upload-build](https://awscli.amazonaws.com/v2/documentation/api/latest/reference/gamelift/upload-build.html) or [CreateBuild()](https://docs.aws.amazon.com/gameliftservers/latest/apireference/API_CreateBuild.html)), set the `ServerSdkVersion` parameter to the 5.x version you're using (this parameter currently defaults to 4.0.2). This parameter must match the actual server SDK libraries in the game server build. If you specify the wrong version for an uploaded game server build, any fleets you create with that build will fail. See [Create a game server build for Amazon GameLift Servers](gamelift-build-cli-uploading.md).

   The following example illustrates how to specify the server SDK version: 

   ```
   aws gamelift upload-build \
       --operating-system AMAZON_LINUX_2023 \
       --server-sdk-version "5.0.0" \
       --build-root "~/mygame" \
       --name "My Game Nightly Build" \
       --build-version "build 255" \
       --region us-west-2
   ```

1. If you use scripts to remotely connect to managed fleets, update the scripts to use the new process, as described in [Connect to fleet instances](fleets-remote-access.md).