# Build a session with Netcode for GameObjects

> Build a multiplayer game with sessions using Netcode for GameObjects for projects with GameObject and MonoBehaviour workflows.

> **Note:**
>
> The Multiplayer Services SDK uses [sessions](/mps-sdk/create-session.md.md) to manage groups of players.
> Sessions relies internally on different combinations of Unity Gaming Services such as [Relay](/relay.md.md), [Distributed Authority](https://unity.com/products/distributed-authority), [Lobby](/lobby.md.md), [Matchmaker](/matchmaker.md.md) and [Cloud Code](/cloud-code.md.md), and thus contributes to the [billing](https://unity.com/solutions/gaming-services/pricing) of those services.

To start a multiplayer game, the host must create a session that other players join to participate in the game. A session represents a group of players that are connected together for a set period of time during a multiplayer game.

To learn the principles of Multiplayer Services sessions, explore a simple multiplayer game of moving capsules. In this tutorial, you create one capsule controlled by the session's host and another capsule controlled by a joining player, as well as the necessary game objects and code to add session management to your game.

## Prerequisites

In addition to the [Multiplayer Services package](../install-and-upgrade), ensure that you install the following packages through the [Unity Registry](https://docs.unity3d.com/6000.0/Documentation/Manual/fs-install.html) in the Editor's Package Manager:

* [Multiplay Sessions Building Block](https://docs.unity3d.com/Manual/building-blocks-multiplayer-sessions.html): Integrates pre-made UI elements as a starting point for your multiplayer projects.
* `Multiplayer Play Mode` (or `com.unity.multiplayer.playmode`): Enables you to test multiplayer functionality without leaving the Unity Editor.
* `Netcode for GameObjects` (or `com.unity.netcode.gameobjects`): Provides networking capabilities to [GameObject](https://docs.unity3d.com/Manual/class-GameObject.html) and [MonoBehaviour](https://docs.unity3d.com/Manual/class-MonoBehaviour.html) workflows.

## Configure Multiplayer Play Mode

To configure Play Mode for your project to test multiple players:

1. In the Unity Editor, go to **Window** > **Multiplayer** > **Multiplayer Play Mode**.
2. In the **Multiplayer Play Mode** window, enable **Player 2**.

After adding Player 2, you can test the project with a second window.

## Set up Netcode for GameObjects

> **Note:**
>
> If you are using Netcode for Entities, [refer to its instructions instead.](../build-with-netcode-for-entities)

To set up Netcode for GameObjects, attach a Network Manager component to a GameObject:

1. In the Unity Editor, select **GameObject** > **Create Empty** to create a new GameObject in your scene.
2. Rename it `NetworkManager`.
3. Select this **NetworkManager** you just created.
4. Select **Component** > **Netcode** > **Network Manager** to attach a Network Manager component.
5. In the **Inspector** window, go to **Network Transport** and select **UnityTransport**.

Netcode for GameObjects is now set up in your project.

## Create the player Prefab

To create a Prefab from a network-enabled capsule:

1. In the Unity Editor, go to **Edit** > **Project Settings** > **Player** > **Other Settings** > **Configuration** > **Active Input Handling**, then select **Both**. Changing the input handling might trigger a restart of your Unity Editor.
2. Close **Project Settings**.
3. Right-click (macOS: **Ctrl**+click) within the **Hierarchy** window, then select **3D Object** > **Capsule**.
4. Rename the capsule to `Player Prefab`.
5. With this capsule selected, in the Inspector window, select **Add Component** > **Netcode** > **Network Object**.
6. In the **Project** tab, right-click (macOS: **Ctrl**+click) the **Scripts** folder, then **Create** > **Scripting** > **Empty C# Script**.
7. Rename this script `PlayerController.cs`.
8. Replace the contents of this script with the following code:
   ```cs
   using UnityEngine;
   using Unity.Netcode;

   public class PlayerController : NetworkBehaviour
   {
       public float speed = 20;

       private NetworkTransform _transform;

       private void Start()
       {
           _transform = GetComponent<NetworkTransform>();
       }
       private void Update()
       {
           if (!IsOwner) return;
           var movement = new Vector3(Input.GetAxis("Horizontal"), Input.GetAxis("Vertical"));
           _transform.transform.position += movement * speed * Time.deltaTime;
       }

   }
   ```
9. With the capsule player selected in the **Hierarchy** window, attach the `PlayerController` script to its **Inspector** window. If you receive a prompt that Network Behaviors require a NetworkObject, select **Yes** to add one.
10. Still in the **Inspector** window, select **Add Component**.
11. Search for `Network Transform`, then add it.
12. Set **Network Transform Authority** to **Client**. This improves the reactiveness of player movement for the owning client. Refer to `NetworkTransform` [Authority](https://docs.unity3d.com/Packages/com.unity.netcode.gameobjects@latest/index.html?subfolder=/manual/components/helper/networktransform.html#authority).
13. In the **Project** window, right-click (macOS: **Ctrl**+click) **Assets**, then **Create** > **Folder**.
14. Rename this folder `Prefabs`. Refer to [Prefabs](https://docs.unity3d.com/Manual/Prefabs.html).
15. Make the `Player Prefab` object you created earlier into a Prefab by dragging it from the **Hierarchy** window into the `Prefabs` folder.
16. Right-click (macOS: **Ctrl**+click) the capsule within the **Scene** window and then select **Delete** to delete the player from the scene.
    > **Tip:**
    >
    > You can remove the player GameObject from the scene because you assigned this network Prefab to the player Prefab property in the `NetworkManager` component. The library doesn't support defining a player object as an in-scene placed NetworkObject.
17. In the **Hierarchy** window, select `NetworkManager`.
18. In its **Inspector** window, locate the **Default Player Prefab** field.
19. Drag the capsule player from the **Project** window into the **Default Player Prefab** field you located.
20. In the Unity Editor, select **File** > **Save**.

At this point, a network-enabled capsule is the default player prefab for the GameObject called `NetworkManager`.

## Add your scene to the build

In **Inspector** window for `NetworkManager`, locate the **Enable Scene Management** setting (enabled by default). When you enable it, the server can control which scenes load for the clients. However, you must add the current scene to the build to enter Play Mode.

To add the current scene to the build:

1. In the Unity Editor, select **File** > **Build Profiles**.
2. Select **Open Scene List**.
3. Select **Add Open Scenes**.
4. Close **Build Profiles**.

The current scene is now included in the build.

## Create and join your session

The following steps outline how to create and join your first session with the [Multiplayer Sessions Building Block](https://docs.unity3d.com/Manual/building-blocks-multiplayer-sessions.html) and Multiplayer Services in the Unity Editor.

> **Note:**
>
> Make sure [Multiplayer Play Mode](#configure-multiplayer-play-mode) is enabled.

1. Follow the [Multiplayer Sessions Building Block](https://docs.unity3d.com/Manual/building-blocks-multiplayer-sessions.html) instructions to integrate its samples into your project.
2. In the Unity Editor's **Project** window, go to `Assets` > `Scenes`.
3. Open the **JoinByCode** scene.
4. In the Toolbar, select **Play** to enter Play Mode.
5. In the **Game** window's **Session Name** field, enter a name, then select **Create**.
6. Copy the session join code.
7. In the **Player 2** window's **Session Code** field, enter the code and then select **Join**.

After Player 2 joins the session, two superimposed capsules appear in the scene.

## Move the capsules

To move the capsules in your multiplayer session:

1. Click within the **Game** window of the Editor.
2. Use the arrow keys on your keyboard to move the capsule around the scene. It moves in real time in both the **Game** window and the **Player 2** window.
3. Click within the **Player 2** window.
4. Use the arrow keys on your keyboard to move the capsule around the scene. Notice that the other capsule (Player 2's capsule) moves this time.

When you enter Play Mode and join the session, you now have a scene of two capsules that can be controlled only by the owning player.