darkstar java game engine for massively multiplayer role-playing games

Project Darkstar is the video game industry's first enterprise grade, high performance, fault tolerant and highly scalable server technology for online, multiplayer games. Project Darkstar has been designed from the ground up to handle almost any kind of online game imaginable.

From card games to full blown MMOGs, Project Darkstar is the perfect technology to get you up and running quickly, allowing you to focus on building your game, not network technologies.

Project Darkstar is designed to provide an environment for game developers that allows scaling through the use of the inherent parallelism found in virtual environments without requiring that the programmers coding such environments learn either distributed computing or multi-threaded programming. Project Darkstar presents an illusion to the programmer that the code for the server side of the application is running on a single machine in a single thread. In fact, the work being done by the server can be spread across any number of machines and threads in a way that allows both increased scaling and fault tolerance. The system is optimized for the low latencies required for game applications.

Available for immediate download, head over to the downloads section and start building your online game today!

Once you have downloaded it, simply unpack it in the directory where you want it to reside.

On Windows, create a system variable named "sgshome" through the "System" control panel. Set the value of the variable to the location of the game server's directory.

On Mac OS X and Linux you need to modify the .bashrc file in your home directory to include the line export SGSHOME=location, where location is the actual location of the game server's directory.

Unlike traditional applications, your game server doesn't have a main(...) method. Instead, Darkstar uses an event-driven model. Your game implements a series of listener interfaces, such as AppListener.

In order to run your game, Darkstar needs to know the name of the class that implements the AppListener interface. This is accomplished through the game properties file.

There are several different listener interfaces used in the Darkstar application server.

These listener interfaces are used in similar manner to the event listeners (e.g.,java.awt.event.ActionListener) in Java GUI programming.

The game properties just a standard Java properties file. Java properties files are text files that contain property definitions. Darkstar requires that four properties be declared:

com.sun.sgs.app.name

The text name of the game. This is can be any string.

com.sun.sgs.app.listener

The name of the main game class which implements the AppListener interface.

com.sun.sgs.app.port

The number of network port on which the server listens for connections.

com.sun.sgs.app.root

The root directory where the game's persistent classes should be saved. See the Managing Game State with Persistent Objects section.

Here is sillygame.properties, a properties file that runs SillyGameMain:

# Silly Game Properties (use # for comments in properties files) com.sun.sgs.app.name=A Silly Game

com.sun.sgs.app.listener=SillyGameMain

com.sun.sgs.app.port=1221

com.sun.sgs.app.root=silly_game_data

import java.io.Serializable;

import java.util.*;

public class SillyGameMain implements AppListener, Serializable

{

// Initialize the game

// prints a message on initialization

public void initialize(Properties properties) {

System.out.println("Game server initialized!");

}

// Handle a client login.

// Prints a message and rejects login by returning null.

public ClientSessionListener loggedIn(ClientSession session) {

System.out.println("Client login attempt!");

return null;

}

}

To compile the code use sgs.jar, which is in the lib directory of the main Darkstar directory.

Once you have created sillygame.properties, you can run your game using the sgs.sh script (sgs.bat on Windows). The script is located in the main game server directory. The script takes two arguments. The first argument is the a classpath that must contain the main game class specified in the com.sun.sgs.app.listener property. The second argument is the properties file, in this case sillygame.properties. For example (assuming that you compiled SillyGameMain into a directory named "classes"):

As the server starts up, it prints a number of status messages, including the message from SillyGameMain's initialize method. The final message indicates that the SillyGame server is successfully up and running. Of course, this silly game rejects all client logins.