Create a session#

To start a multiplayer game, the host must create a session that other players join to participate in the game. This page outlines what you must include in your script to create a session. Consider the following factors when you create a session:

• The session options properties
• The type of network connection

using Unity.Services.Multiplayer;

The CreateOrJoinSessionAsync method#

The CreateOrJoinSessionAsync method either joins the session with the given ID, or if it does not exist, creates the session. This is convenient in cases where race condition can happen between clients and you are not sure which client will create the session.

var session = await MultiplayerService.Instance.CreateOrJoinSessionAsync(sessionId, options)

Session options properties#

The session options determine various properties of your session, such as the maximum number of players or whether the session is password protected.

Refer to Class SessionOptions for a full list of options.

Type of network connection#

Another consideration for your session is the network connection type with which the players join the session. Players can join with a direct network connection, or via a client hosted solution provided by Unity (Relay or Distributed Authority) Using one of our client hosted solutions for network connection provides the most compatibility, and is the recommended best practice for peer-to-peer games played over the Internet.

Refer to Class SessionOptions > Methods for more information.

Example#

Consider the following example code you might add to your script to create a session with a Unity client-hosted solution.

async void StartSessionAsHost()
{
    var options = new SessionOptions
    {
      MaxPlayers = 2
    }.WithRelayNetwork(); // or WithDistributedAuthorityNetwork() to use Distributed Authority instead of Relay
    var session = await MultiplayerService.Instance.CreateSessionAsync(options);
    Debug.Log($"Session {session.Id} created! Join code: {session.Code}");
}

In this code:

• The variable MaxPlayers sets the maximum number of players allowed in the session, including the host. In this example, the maximum number of players is two.
• The variable options of class SessionOptions can determine other session options, such as the session’s name, and whether it is password protected.
• The use of WithRelayNetwork() (or WithDistributedAuthorityNetwork()) configures the session to use Relay (or Distributed Authority) networking rather than direct connections (in other words, with a fixed IP address and port). This is the recommended best practice for peer-to-peer connectivity over the Internet. Refer to Relay or Distributed Authority.
• The line var session = await MultiplayerService.Instance.CreateSessionAsync(options); creates the session, and makes the player the host.
• The final line, Debug.Log($"Session {session.Id} created! Join code: {session.Code}");, displays the session ID and join code in the console of the Unity Editor. The host would then share this join code with the other players. Alternatively, you could create a variable to get the join code, as in var joinCode = session.Code; and use that variable instead.

Advanced usage: Specifying a custom network handler#

It is possible to specify a custom network handler implementing INetworkHandler, overriding the default integration with Netcode for Game Objects and Netcode for Entities.

var options = new SessionOptions { MaxPlayers = 2 }
        .WithRelayNetwork()
        .WithNetworkHandler(new CustomEntitiesNetworkHandler());