Lobby and matchmaking basics in Unity

Introduction

A lobby lets players gather before a game starts. Matchmaking helps find players to play together or against each other.

When you want players to join a waiting room before a multiplayer game.

When you want to connect players with similar skill levels automatically.

When you want to create teams or groups for a game session.

When you want to manage who joins a game and when it starts.

When you want to let players invite friends to play together.

Syntax

Unity

using UnityEngine;
using UnityEngine.Networking;

public class LobbyManager : NetworkLobbyManager
{
    // Override methods to customize lobby behavior
    public override void OnLobbyClientEnter()
    {
        Debug.Log("Player joined the lobby");
    }

    public override GameObject OnLobbyServerCreateLobbyPlayer(NetworkConnection conn, short playerControllerId)
    {
        Debug.Log("Creating lobby player");
        return base.OnLobbyServerCreateLobbyPlayer(conn, playerControllerId);
    }
}

Unity uses NetworkLobbyManager to handle lobby and matchmaking basics.

You can override methods to customize what happens when players join or leave.

Examples

This runs when a player joins the lobby and prints a message.

Unity

public override void OnLobbyClientEnter()
{
    Debug.Log("A new player has entered the lobby.");
}

This runs when the server creates a player in the lobby.

Unity

public override GameObject OnLobbyServerCreateLobbyPlayer(NetworkConnection conn, short playerControllerId)
{
    Debug.Log("Lobby player created.");
    return base.OnLobbyServerCreateLobbyPlayer(conn, playerControllerId);
}

Sample Program

This simple lobby manager logs when players join and starts the game when all are ready.

Unity

using UnityEngine;
using UnityEngine.Networking;

public class SimpleLobby : NetworkLobbyManager
{
    public override void OnLobbyClientEnter()
    {
        Debug.Log($"Player connected: {NetworkClient.connection.connectionId}");
    }

    public override void OnLobbyServerPlayersReady()
    {
        Debug.Log("All players are ready. Starting game...");
        ServerChangeScene(playScene);
    }
}

Important Notes

Matchmaking often requires a server or service to connect players.

Unity's built-in networking is deprecated; consider using newer solutions like Mirror or Unity Relay.

Always test lobbies with multiple players to ensure smooth joining and starting.

Summary

Lobbies let players wait and prepare before a game.

Matchmaking finds and connects players automatically.

Override lobby methods to customize player joining and game start.

Practice

1. What is the main purpose of a lobby in Unity multiplayer games?

easy

A. To let players wait and prepare before the game starts

B. To automatically find and connect players

C. To render 3D graphics for the game

D. To save player progress locally

Solution

1. Step 1: Understand the role of a lobby

   A lobby is a waiting area where players gather before the game begins.

2. Step 2: Differentiate from matchmaking

   Matchmaking is the process of finding and connecting players automatically, not the lobby itself.

3. Final Answer:

   To let players wait and prepare before the game starts -> Option A

4. Quick Check:

   Lobby = waiting area before game [OK]

Hint: Lobbies are for waiting; matchmaking is for finding players [OK]

Common Mistakes:

• Confusing lobby with matchmaking
• Thinking lobby handles graphics
• Assuming lobby saves progress

2. Which of the following is the correct way to override a lobby method in Unity C#?

easy

A. public override void OnPlayerJoined() {}

B. override public void OnPlayerJoined() {}

C. public void OnPlayerJoined() override {}

D. void override OnPlayerJoined() {}

Solution

1. Step 1: Recall C# override syntax

   In C#, the correct syntax places 'override' before the return type.

2. Step 2: Check each option

   public override void OnPlayerJoined() {} uses 'public override void MethodName()' which is correct syntax.

3. Final Answer:

   public override void OnPlayerJoined() {} -> Option A

4. Quick Check:

   Override keyword before return type [OK]

Hint: In C#, 'override' comes before the return type [OK]

Common Mistakes:

• Placing override after method name
• Omitting override keyword
• Wrong order of keywords

3. Given this code snippet in a Unity lobby script:

public override void OnPlayerJoined(Player player) {
    Debug.Log($"Player {player.Name} joined.");
    if (Players.Count >= 4) {
        StartGame();
    }
}

What happens when the 4th player joins?

medium

A. The lobby closes without starting the game

B. Nothing happens until manually started

C. The game starts automatically

D. An error occurs because Players.Count is undefined

Solution

1. Step 1: Analyze the OnPlayerJoined method

   When a player joins, it logs their name and checks if Players.Count is 4 or more.

2. Step 2: Understand the condition

   If Players.Count is 4 or more, StartGame() is called, starting the game automatically.

3. Final Answer:

   The game starts automatically -> Option C

4. Quick Check:

   Players.Count >= 4 triggers StartGame() [OK]

Hint: Check conditions that trigger StartGame() call [OK]

Common Mistakes:

• Assuming manual start needed
• Thinking Players.Count is undefined
• Confusing lobby closing with game start

4. Identify the error in this matchmaking code snippet:

public void Matchmake() {
    var match = Matchmaker.CreateMatch();
    match.OnPlayerJoined += OnPlayerJoined;
    match.Start();
}

void OnPlayerJoined(Player player) {
    Debug.Log("Player joined: " + player.Name);
}

medium

A. Start() method does not exist on match object

B. Event subscription syntax is incorrect

C. OnPlayerJoined method must be public to subscribe

D. Matchmaker.CreateMatch() might return null and is not checked

Solution

1. Step 1: Review event subscription

   The syntax 'match.OnPlayerJoined += OnPlayerJoined;' is correct for subscribing to events.

2. Step 2: Check for null safety

   Matchmaker.CreateMatch() might return null if no match is found, but code does not check for null before using match.

3. Final Answer:

   Matchmaker.CreateMatch() might return null and is not checked -> Option D

4. Quick Check:

   Always check for null after CreateMatch() [OK]

Hint: Always check if CreateMatch() returns null before use [OK]

Common Mistakes:

• Assuming event subscription syntax is wrong
• Ignoring null checks
• Assuming Start() method is missing

5. You want to create a lobby that only starts the game when all players are ready. Which approach is best in Unity matchmaking?

hard

A. Call StartGame() immediately when the first player joins

B. Override OnPlayerJoined to check a 'ready' flag on each player before calling StartGame()

C. Use a timer to start the game after 30 seconds regardless of players

D. Disable matchmaking and start game manually from UI

Solution

1. Step 1: Understand the requirement

   The game should start only when all players are ready, not just when they join.

2. Step 2: Choose the best method

   Overriding OnPlayerJoined to check each player's 'ready' status before starting the game ensures all are prepared.

3. Final Answer:

   Override OnPlayerJoined to check a 'ready' flag on each player before calling StartGame() -> Option B

4. Quick Check:

   Check readiness before starting game [OK]

Hint: Check all players' ready flags before starting game [OK]

Common Mistakes:

• Starting game too early
• Ignoring player readiness
• Disabling matchmaking unnecessarily