How to convert a single-player game to Multiplayer in Unity?

This post describes steps to converting a single player game to a multiplayer game, using the new Unity Multiplayer networking system. The process described here is a simplified, higher level version of the actual process for a real game; it doesn’t always work exactly like this, but it provides a basic recipe for the process.

NetworkManager set-up

• Add a new GameObject to the Scene and rename it “NetworkManager”.
• Add the NetworkManager component to the “NetworkManager” GameObject.
• Add the NetworkManagerHUD component to the GameObject. This provides the default UI for managing the network game state.

Player Prefab set-up

• Find the Prefab for the player GameObject in the game, or create a Prefab from the player GameObject
• Add the NetworkIdentity component to the player Prefab
• Check the LocalPlayerAuthority box on the NetworkIdentity
• Set the playerPrefab in the NetworkManager’s Spawn Info section to the player Prefab
• Remove the player GameObject instance from the Scene if it exists in the Scene

Player movement

• Add a NetworkTransform component to the player Prefab
• Update input and control scripts to respect isLocalPlayer
• Fix Camera to use spawned player and isLocalPlayer

For example, this script only processes input for the local player:

using UnityEngine;
using UnityEngine.Networking;

public class Controls : NetworkBehaviour
{
    void Update()
    {
        if (!isLocalPlayer)
        {
            // exit from update if this is not the local player
            return;
        }

        // handle player input for movement
    }
}

Basic player game state

• Make scripts that contain important data into NetworkBehaviours instead of MonoBehaviours
• Make important member variables into SyncVars

Networked actions

• Make scripts that perform important actions into NetworkBehaviours instead of MonoBehaviours
• Update functions that perform important player actions to be commands

*Non-player GameObjects *

Fix non-player prefabs such as enemies:

• Add the NetworkIdentify component
• Add the NetworkTransform component
• Register spawnable Prefabs with the NetworkManager
• Update scripts with game state and actions

Spawners

• Potentially change spawner scripts to be NetworkBehaviours
• Modify spawners to only run on the server (use isServer property or the OnStartServer() function)
• Call NetworkServer.Spawn() for created GameObjects

Spawn positions for players

• Add a new GameObject and place it at player’s start location
• Add the NetworkStartPosition component to the new GameObject

Lobby

• Create Lobby Scene
• Add a new GameObject to the Scene and rename it to “NetworkLobbyManager”.
• Add the NetworkLobbyManager component to the new GameObject.
• Configure the Manager: Scenes Prefabs Spawners