Lobby and matchmaking basics in Unity - Mini Project: Build & Apply

Lobby and Matchmaking Basics

📖 Scenario: You are creating a simple multiplayer game lobby where players can join and be matched into a game room. This is a common feature in online games where players wait in a lobby before starting a match.

🎯 Goal: Build a basic lobby system that stores player names, sets a maximum number of players per room, matches players into rooms, and displays the matched rooms.

📋 What You'll Learn

Create a list to store player names

Create a variable for maximum players per room

Write logic to group players into rooms based on the max players

Print the list of rooms with their players

💡 Why This Matters

🌍 Real World

Game developers use lobbies and matchmaking to organize players into game sessions smoothly.

💼 Career

Understanding lobby and matchmaking basics is essential for multiplayer game programming roles.

1

Create the player list

Create a List<string> called players and add these exact player names: "Alice", "Bob", "Charlie", "Diana", "Ethan", "Fiona".

Unity

# Create a List called players and add the given names
// Your code here

Hint

Use new List<string> { ... } to create the list with the exact player names.

2

Set maximum players per room

Create an int variable called maxPlayersPerRoom and set it to 3.

Unity

using System.Collections.Generic;

List players = new List { "Alice", "Bob", "Charlie", "Diana", "Ethan", "Fiona" };

// Create an int variable maxPlayersPerRoom and set it to 3
// Your code here

Hint

Just declare an integer variable with the exact name and value.

3

Group players into rooms

Create a List<List<string>> called rooms. Use a for loop with variable i to group players from players into rooms of size maxPlayersPerRoom. Add each group as a new list to rooms.

Unity

using System.Collections.Generic;

List players = new List { "Alice", "Bob", "Charlie", "Diana", "Ethan", "Fiona" };

int maxPlayersPerRoom = 3;

// Create a List> called rooms
// Use a for loop with i to group players into rooms
// Your code here

Hint

Use players.GetRange(i, Math.Min(maxPlayersPerRoom, players.Count - i)) inside the loop to get each room's players.

4

Display the rooms and players

Use a for loop with variable roomIndex to print each room number starting from 1. Inside it, use a foreach loop with variable player to print each player's name in that room. Use System.Console.WriteLine for printing.

Unity

using System.Collections.Generic;

List players = new List { "Alice", "Bob", "Charlie", "Diana", "Ethan", "Fiona" };

int maxPlayersPerRoom = 3;

List> rooms = new List>();

for (int i = 0; i  room = players.GetRange(i, System.Math.Min(maxPlayersPerRoom, players.Count - i));
    rooms.Add(room);
}

// Print each room and its players
// Your code here

Hint

Use nested loops: outer loop for rooms, inner loop for players. Use Console.WriteLine with string interpolation to print.

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