To better understand this book, we'll need to cover the basic features of the Unity IDE.

If you open Unity for the first time, you'll be presented with a window where you can either open an existing project or create a new one. Select the Create New Project tab, and choose a location for your project.

Once your project is created, you'll see a number of panels. There are the Scene and Game tabs, the Hierarchy, Project, and Console tabs, and the Inspector tab.

The Scene view shows the current scene. This will allow you to navigate the scene, select objects, move them around, and more. The Game view shows the view of the main camera. If you press the Play button, the Game view is automatically shown and allows you to play test your game from inside the editor.

The Hierarchy tab shows the object hierarchy of the current scene. This allows you to select objects, parent or unparent them, delete them, rename them, and much more.

The Inspector tab shows the editors for each component attached to the selected object (rather than being inheritance based like many traditional engines, Unity is component based, where objects are a collection of components and each component has a separate responsibility). It allows you to set values and change properties of components. You can also remove components by right clicking on a component and clicking on Remove Component. In Unity 4 and later, you can also click on the Add Component button and select a component script.

The Project tab shows the assets in your project. You can drop game assets here to import them, and you can create new materials, scripts, and shaders by right-clicking and selecting the Create option. You can also drag objects from the Hierarchy to the Project tab to create a prefab. Prefabs are essentially object templates—you can Instantiate a prefab to create an exact copy of the prefab in the scene (for instance, you might create an Enemy prefab, and instantiate it to spawn enemies). You can also drag component scripts from the Project to the Inspector of a selected game object to add the component to the object.

To learn more about Unity, you can get started here:

http://unity3d.com/learn

Chapter 1, Unity Networking – The Pong Game, introduces the concept of reliable UDP communication, and different types of servers employed by games. It covers Unity Networking, and creating a networked two-player Pong clone.

Chapter 2, Photon Unity Networking – The Chat Client, covers a third-party alternative to Unity Networking. It introduces the concept of the cloud-hosted game servers, simple matchmaking, and friends lists. It also covers the creation of a simple chat client.

Chapter 3, Photon Server – Star Collector, introduces dedicated servers for games. It covers creating a Photon Server application, connecting to a server, using the request/response/event system to communicate, and creating a simple Star Collector game.

Chapter 4, Player.IO – Bot Wars, covers an alternative dedicated server system. It introduces the database features of Player.IO, how to create a Player.IO server, connecting from Unity, and creating a simple RTS-style game with persistent user stats.

Chapter 5, PubNub – The Global Chatbox, introduces communication over an HTTP messaging service. It covers benefits and pitfalls of HTTP for communication, using the WWW class to communicate via PubNub, and creating a chatroom application.

Chapter 6, Entity Interpolation and Prediction, introduces the concept of server-side movement physics and potential issues and solutions. It covers client-side movement prediction, and how to smooth the motion of remote entities.

Chapter 7, Server-side Hit Detection, introduces the concept of server-side hit detection for shooter-style games. It covers the reasons behind target-leading problems in many online games, and how to resolve the issue by rewinding the game state.

You will need Unity 3 or later for this book. Many chapters require specific downloads:

Instructions to download the required materials are covered at the beginning of each chapter.

This book is for developers who want to get started writing multiplayer games with the Unity game engine. Readers are expected to have a working knowledge of C#. Knowledge of the Unity IDE is helpful, but not strictly required.

In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

Code words in text are shown as follows: "Navigate to the Release folder and run the EXE."

A block of code is set as follows:

public class ExampleUnityNetworkSerializePosition : MonoBehaviour
{
  public void OnSerializeNetworkView( BitStream stream, NetworkMessageInfo info )
  {
    // we are currently writing information to the network
    if( stream.isWriting )
    {
      // send the object's position
      Vector3 position = transform.position;
      stream.Serialize( ref position );
    }

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

// the maximum score a player can reach
  public int ScoreLimit = 10;

  // the display test for player 1's score
  public TextMesh Player1ScoreDisplay;

  // the display text for player 2's score
  public TextMesh Player2ScoreDisplay;

  // Player 1's score
  private int p1Score = 0;

New terms and important words are shown in bold. Words that you see on the screen, in menus, or dialog boxes for example, appear in the text like this: "clicking the Next button moves you to the next screen".

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