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NetworkManager

The NetworkManager is a required Netcode for GameObjects (Netcode) component that contains all of your project's netcode related settings. Think of it as the "central netcode hub" for your netcode enabled project.

NetworkManager Inspector Properties#

  • LogLevel: Sets the network logging level
  • PlayerPrefab: When a prefab is assigned, the prefab will be instantiated as the player object and assigned to the newly connected and authorized client.
  • NetworkPrefabs: Where you register your network prefabs. You can also create a single network prefab override per registered network prefab here.
  • Protocol Version: Set this value to help distinguish between builds when the most current build has new assets that could cause issues with older builds connecting.
  • Network Transport: Where your network specific settings and transport type is set. This field accepts any INetworkTransport implementation. However, unless you have unique transport specific needs UnityTransport is the recommended transport to use with Netcode for GameObjects.
  • Tick Rate: This value controls the network tick update rate.
  • Ensure Network Variable Length Safety: (Increases cpu processing and bandwidth) When this property is checked, Netcode for GameObjects will prevent user code from writing past the boundaries of a NetworkVariable.
  • Connection Approval: This enables connection approval when this is checked and the NetworkManager.ConnectionApprovalCallback is assigned.
  • Client Connection Buffer Timeout: This value sets the amount of time that has to pass for a connecting client to complete the connection approval process. If the time specified is exceeded the connecting client will be disconnected.
  • Force Same Prefabs: When checked it will always verify that connecting clients have the same registered network prefabs as the server. When not checked, Netcode for GameObjects will ignore any differences.
  • Recycle Network Ids: When checked this will re-use previously assigned NetworkObject.NetworkObjectIds after the specified period of time.
  • Network Id Recycle Delay: The time it takes for a previously assigned but currently unassigned identifier to be available for use.
  • Enable Scene Management: When checked Netcode for GameObjects will handle scene management and client synchronization for you. When not checked, users will have to create their own scene management scripts and handle client synchronization.
  • Load Scene Time Out: When Enable Scene Management is checked, this specifies the period of time the NetworkSceneManager will wait while a scene is being loaded asynchronously before NetworkSceneManager considers the load/unload scene event to have failed/timed out.

NetworkManager Sub-Systems#

NetworkManager is also where you can find references to other Netcode related management systems:

caution

All NetworkManager sub-systems are instantiated once the NetworkManager is started (i.e. NetworkManager.IsListening == true). A good general "rule of thumb" is to not attempt to access the below sub-systems prior to starting the NetworkManager, otherwise they will not yet be initialized.

Starting a Server, Host, or Client#

In order to perform any netcode related action that involves sending messages, you must first have a server started and listening for connections with at least one client (a server can send RPCs to itself when running as a host) that is connected. In order to accomplish this, you must first start your NetworkManager as a server, host, or client. There are three NetworkManager methods you can invoke to accomplish this:

NetworkManager.Singleton.StartServer(); // Starts the NetworkManager as just a server (i.e. no local client).
NetworkManager.Singleton.StartHost(); // Starts the NetworkManager as both a server and a client (i.e. has local client)
NetworkManager.Singleton.StartClient(); // Starts the NetworkManager as just a client.
warning

Do not start a NetworkManager within a NetworkBehaviour's Awake method as this can lead to undesirable results depending upon your project's settings!

note

When starting a Server or joining an already started session as client, the NetworkManager can spawn a "Player Object" belonging to the client.

For more information about player prefabs see:

Connecting#

When Starting a Client, the NetworkManager uses the IP and the Port provided in your Transport component for connecting. While you can set the IP address in the editor, many times you might want to be able to set the IP address and port during runtime.

The below examples use Unity Transport to demonstrate a few ways you can gain access to the UnityTransport component via the NetworkManager.Singleton in order to configure your project's network settings programmatically:

If you are only setting the IP address and port number, then you can use the UnityTransport.SetConnectionData method:

NetworkManager.Singleton.GetComponent<UnityTransport>().SetConnectionData(
"127.0.0.1", // The IP address is a string
(ushort)12345 // The port number is an unsigned short
);

If you are using the same code block to configure both your server and your client and you want to configure your server to listen to all IP addresses assigned to it, then you can also pass a 'listen address' of "0.0.0.0" to the SetConnectionData method, like so:

NetworkManager.Singleton.GetComponent<UnityTransport>().SetConnectionData(
"127.0.0.1", // The IP address is a string
(ushort)12345, // The port number is an unsigned short
"0.0.0.0" // The server listen address is a string.
);
note

Using an IP address of 0.0.0.0 for the server listen address will make a server or host listen on all IP addresses assigned to the local system. This can be particularly helpful if you are testing a client instance on the same system as well as one or more client instances connecting from other systems on your local area network. Another scenario is while developing and debugging you might sometimes test local client instances on the same system and sometimes test client instances running on external systems.

It is possible to access the current connection data at runtime, via NetworkManager.Singleton.GetComponent<UnityTransport>().ConnectionData. This will return a ConnectionAddressData struct, holding this info. You are strongly advised to use the SetConnectionData method to update this info.

If you are using Unity Relay to handle connections, however, do not use SetConnectionData. The host should call SetHostRelayData, and clients should call SetClientRelayData. Attempting to join a Relay-hosted game via entering IP/port number (via SetConnectionData) will not work.

More information about Netcode for GameObjects Transports

Disconnecting and Shutting Down#

Disconnecting is rather simple, but you cannot use/access any subsystems (i.e. NetworkSceneManager) once the NetworkManager is stopped because they will no longer be available. For client, host, or server modes, you only need to call the NetworkManager.Shutdown method as it will disconnect while shutting down.

info

When no network session is active and the NetworkManager has been shutdown, you will need to use UnityEngine.SceneManagement to load any non-network session related scene.

public void Disconnect()
{
NetworkManager.Singleton.Shutdown();
// At this point we must use the UnityEngine's SceneManager to switch back to the MainMenu
UnityEngine.SceneManagement.SceneManager.LoadScene("MainMenu");
}

Disconnecting Clients (Server Only)#

At times you might need to disconnect a client for various reasons without shutting down the server. To do this, you can call the NetworkManager.DisconnectClient method while passing the identifier of the client you wish to disconnect as the only parameter. The client identifier can be found within:

  • The NetworkManager.ConnectedClients dictionary that uses the client identifier as a key and the value as the NetworkClient.
  • As a read only list of NetworkClients via the NetworkManager.ConnectedClientsList.
  • A full list of all connected client identifiers can be accessed via NetworkManager.ConnectedClientsIds.
  • The client identifier is passed as a parameter to all subscribers of the NetworkManager.OnClientConnected event.
  • The player's NetworkObject has the NetworkObject.OwnerClientId property.
tip

One way to get a player's primary NetworkObject is via NetworkClient.PlayerObject.

void DisconnectPlayer(NetworkObject player)
{
// Note: If a client invokes this method, it will throw an exception.
NetworkManager.DisconnectClient(player.OwnerClientId);
}

Client Disconnection Notifications#

Both the client and the server can subscribe to the NetworkManger.OnClientDisconnectCallback event in order to be notified when a client is disconnected. Client disconnect notifications are "relative" to who is receiving the notification.

There are two general "disconnection" categories:

  • Logical: Custom server side code (code you might have written for your project) invokes NetworkManager.DisconnectClient.
    • Example: A host player might eject a player or a player becomes "inactive" for too long.
  • Network Interruption: The transport detects there is no longer a valid network connection.

When disconnect notifications are triggered:

  • Clients are notified when they are disconnected by the server.
  • The server is notified if the client side disconnects (i.e. a player exits a game session)
  • Both the server and clients are notified when their network connection is disconnected (network interruption)

Scenarios where the disconnect notification will not be triggered:

  • When a server "logically" disconnects a client.
    • Reason: The server already knows the client is disconnected.
  • When a client "logically" disconnects itself.
    • Reason: The client already knows that it is disconnected.

Connection Notification Manager Example#

Below is one example of how you could provide client connect and disconnect notifications to any type of NetworkBehaviour or MonoBehaviour derived component.

important

The ConnectionNotificationManager example below should only be attached to the same GameObject as NetworkManager to assure it persists as long as the NetworkManager.Singleton instance.

using System;
using UnityEngine;
using Unity.Netcode;
/// <summary>
/// Only attach this example component to the NetworkManager GameObject.
/// This will provide you with a single location to register for client
/// connect and disconnect events.
/// </summary>
public class ConnectionNotificationManager : MonoBehaviour
{
public static ConnectionNotificationManager Singleton { get; internal set; }
public enum ConnectionStatus
{
Connected,
Disconnected
}
/// <summary>
/// This action is invoked whenever a client connects or disconnects from the game.
/// The first parameter is the ID of the client (ulong).
/// The second parameter is whether or not that client is connecting or disconnecting.
/// </summary>
public event Action<ulong, ConnectionStatus> OnClientConnectionNotification;
private void Awake()
{
if (Singleton != null)
{
// As long as you aren't creating multiple NetworkManager instances, throw an exception.
// (***the current position of the callstack will stop here***)
throw new Exception($"Detected more than one instance of {nameof(ConnectionNotificationManager)}! " +
$"Do you have more than one component attached to a {nameof(GameObject)}");
}
Singleton = this;
}
private void Start()
{
if (Singleton != this){
return; // so things don't get even more broken if this is a duplicate >:(
}
if (NetworkManager.Singleton == null)
{
// Can't listen to something that doesn't exist >:(
throw new Exception($"There is no {nameof(NetworkManager)} for the {nameof(ConnectionNotificationManager)} to do stuff with! " +
$"Please add a {nameof(NetworkManager)} to the scene.");
}
NetworkManager.Singleton.OnClientConnectedCallback += OnClientConnectedCallback;
NetworkManager.Singleton.OnClientDisconnectCallback += OnClientDisconnectCallback;
}
private void OnDestroy()
{
// Since the NetworkManager could potentially be destroyed before this component, only
// remove the subscriptions if that singleton still exists.
if (NetworkManager.Singleton != null)
{
NetworkManager.Singleton.OnClientConnectedCallback -= OnClientConnectedCallback;
NetworkManager.Singleton.OnClientDisconnectCallback -= OnClientDisconnectCallback;
}
}
private void OnClientConnectedCallback(ulong clientId)
{
OnClientConnectionNotification?.Invoke(clientId, ConnectionStatus.Connected);
}
private void OnClientDisconnectCallback(ulong clientId)
{
OnClientConnectionNotification?.Invoke(clientId, ConnectionStatus.Disconnected);
}
}