网络编程之：UDP服务器

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

/**
 * UDP服务器
 * 
 */
public abstract class UDPServer implements Runnable {
	// *********常数*********

	private static final int MAX_BUFFER_SIZE = 8096;// 8k
	private static final int DEFAULT_PORT = 9090;

	// *********成员变量*********

	private int bufferSize;
	protected DatagramSocket socket;
	private Thread runner = null;
	private volatile boolean shouldStop = false;

	// *********构造函数*********

	/**
	 * 使用默认监听端口(9090)和默认的接收缓存大小(8096字节)构建一个UDPServer对象。
	 * 
	 */
	protected UDPServer() throws SocketException {
		this(DEFAULT_PORT, MAX_BUFFER_SIZE);
	}

	/**
	 * 
	 * 构建一个UDPServer对象。使用默认的接收缓存大小(8096字节)
	 * 
	 * @param port 服务监听端口
	 * @throws SocketException
	 */
	protected UDPServer(int port) throws SocketException {
		this(port, MAX_BUFFER_SIZE);
	}

	/**
	 * 
	 * 构建一个UDPServer对象。
	 * 
	 * @param port 服务监听端口
	 * @param bufferSize 接收缓存大小（单位字节）
	 * @throws SocketException 端口被占用或没有权限时抛出的例外
	 */
	protected UDPServer(int port, int bufferSize) throws SocketException {
		this.bufferSize = bufferSize;
		this.socket = new DatagramSocket(port);
	}

	// *********成员方法*********

	/**
	 * 开始UDP服务
	 */
	public synchronized void start() {
		if (runner == null) {
			runner = new Thread(this);
			runner.setDaemon(false);
			runner.start();
		}
	}

	/**
	 * 停止UDP服务
	 */
	public synchronized void stop() {
		if (socket != null) {
			shouldStop = true;
			runner.interrupt();
			runner = null;
			socket.close();
			socket = null;
		}
	}

	/**
	 * (non-Javadoc)
	 * 
	 * @see java.lang.Runnable#run()
	 */
	public void run() {
		byte[] buffer = new byte[bufferSize];
		while (!shouldStop) {
			DatagramPacket input = new DatagramPacket(buffer, buffer.length);
			try {
				socket.receive(input);
				requestHandle(input);
			} catch (IOException ioe) {
				// igonre
			}
		}
	}

	/**
	 * 处理UDP请求
	 * 
	 * @param input UDP数据报
	 */
	public abstract void requestHandle(DatagramPacket input);

}