Mirror/doc/articles/Concepts/GameObjects/SpawnPlayerCustom.md

Custom Player Spawning

The Network Manager offers a built-in simple player spawning feature, however you may want to customize the player spawning process - for example to assign a color to each new player spawned.

To do this you need to override the default behavior of the Network Manager with your own script.

When the Network Manager adds a player, it also instantiates a game object from the Player Prefab and associates it with the connection. To do this, the Network Manager calls NetworkServer.AddPlayerForConnection. You can modify this behavior by overriding NetworkManager.OnServerAddPlayer. The default implementation of OnServerAddPlayer instantiates a new player instance from the player Prefab and calls NetworkServer.AddPlayerForConnection to spawn the new player instance. Your custom implementation of OnServerAddPlayer must also call NetworkServer.AddPlayerForConnection, but your are free to perform any other initialization you require in that method too.

The example below customizes the color of a player. First, add the Player script to the player prefab:

using UnityEngine;
using Mirror;
class Player : NetworkBehaviour
{
    [SyncVar]
    public Color color;
}

Next, create a custom Network Manager to handle spawning.

using UnityEngine;
using Mirror;

public class MyNetworkManager : NetworkManager
{
    public override void OnServerAddPlayer(NetworkConnection conn, AddPlayerMessage extraMessage)
    {
        GameObject player = Instantiate(playerPrefab);
        player.GetComponent<Player>().color = Color.red;
        NetworkServer.AddPlayerForConnection(conn, player);
    }
}

The function NetworkServer.AddPlayerForConnection does not have to be called from within OnServerAddPlayer. As long as the correct connection object and playerControllerId are passed in, it can be called after OnServerAddPlayer has returned. This allows asynchronous steps to happen in between, such as loading player data from a remote data source.

The system automatically spawns the player game object passed to NetworkServer.AddPlayerForConnection on the server, so you don’t need to call NetworkServer.Spawn for the player. Once a player is ready, the active networked game objects (that is, game objects with an associated NetworkIdentity) in the Scene spawn on the player’s client. All networked game objects in the game are created on that client with their latest state, so they are in sync with the other participants of the game.

You don’t need to use playerPrefab on the NetworkManager to create player game objects. You could use different methods of creating different players.

Ready State

In addition to players, client connections also have a “ready” state. The host sends clients that are ready information about spawned game objects and state synchronization updates; clients which are not ready are not sent these updates. When a client initially connects to a server, it is not ready. While in this non-ready state, the client can do things that don’t require real-time interactions with the game state on the server, such as loading Scenes, allowing the player to choose an avatar, or fill in log-in boxes. Once a client has completed all its pre-game work, and all its Assets are loaded, it can call ClientScene.Ready to enter the “ready” state. The simple example above demonstrates implementation of ready states; because adding a player with NetworkServer.AddPlayerForConnection also puts the client into the ready state if it is not already in that state.

Clients can send and receive network messages without being ready, which also means they can do so without having an active player game object. So a client at a menu or selection screen can connect to the game and interact with it, even though they have no player game object. See documentation on Network Messages for more details about sending messages without using commands and RPC calls.

Switching Players

To replace the player game object for a connection, use NetworkServer.ReplacePlayerForConnection. This is useful for restricting the commands that players can issue at certain times, such as in a pregame lobby screen. This function takes the same arguments as AddPlayerForConnection, but allows there to already be a player for that connection. The old player game object does not have to be destroyed. The NetworkLobbyManager uses this technique to switch from the NetworkLobbyPlayer game object to a game play player game object when all the players in the lobby are ready.

You can also use ReplacePlayerForConnection to respawn a player or change the object that represents the player. In some cases it is better to just disable a game object and reset its game attributes on respawn. The following code sample demonstrates how to actually replace the player game object with a new game object:

public class MyNetworkManager : NetworkManager
{
    public void ReplacePlayer(GameObject newPrefab)
    {
        NetworkConnection conn = NetworkClient.connection;

        // Cache a reference to the current player object
        GameObject oldPlayer = conn.playerController.gameObject;

        // Instantiate the new player object and broadcast to clients
        NetworkServer.ReplacePlayerForConnection(conn, Instantiate(newPrefab));

        // Remove the previous player object that's now been replaced
        NetworkServer.Destroy(oldPlayer);
    }
}

If the player game object for a connection is destroyed, then that client cannot execute Commands. They can, however, still send network messages.

To use ReplacePlayerForConnection you must have the NetworkConnection game object for the player’s client to establish the relationship between the game object and the client. This is usually the property connectionToClient on the NetworkBehaviour class, but if the old player has already been destroyed, then that might not be readily available.

To find the connection, there are some lists available. If using the NetworkLobbyManager, then the lobby players are available in lobbySlots. The NetworkServer also has lists of connections.