import java.awt.*;
import java.net.*;
import java.io.*;
import java.util.*;
/**
 * Description:
 * <br/>Copyright (C), 2008-2010, Yeeku.H.Lee
 * <br/>This program is protected by copyright laws.
 * <br/>Program Name:
 * <br/>Date:
 * @author  Yeeku.H.Lee kongyeeku@163.com
 * @version  1.0
 */
//讓該類實現Runnable接口，該類的實例可作為線程的target
public class MulticastSocketTest implements Runnable
{
	//使用常量作為本程序的多點廣播IP地址
	private static final String BROADCAST_IP
		= "230.0.0.1";
	//使用常量作為本程序的多點廣播目的的端口
	public static final int BROADCAST_PORT = 30000;
	//定義每個數據報的最大大小為4K
	private static final int DATA_LEN = 4096;

	
	//定義本程序的MulticastSocket實例
	private MulticastSocket socket = null;
	private InetAddress broadcastAddress = null;
	private Scanner scan = null;
	//定義接收網絡數據的字節數組
	byte[] inBuff = new byte[DATA_LEN];
	//以指定字節數組創建準備接受數據的DatagramPacket對象
	private DatagramPacket inPacket = 
		new DatagramPacket(inBuff , inBuff.length);
	//定義一個用于發送的DatagramPacket對象
	private DatagramPacket outPacket = null;
	public void init()throws IOException
	{
		try
		{
			//創建用于發送、接收數據的MulticastSocket對象
			//因為該MulticastSocket對象需要接收，所以有指定端口
			socket = new MulticastSocket(BROADCAST_PORT);
			broadcastAddress = InetAddress.getByName(BROADCAST_IP);
			//將該socket加入指定的多點廣播地址
			socket.joinGroup(broadcastAddress);
			//設置本MulticastSocket發送的數據報被回送到自身
			socket.setLoopbackMode(false);
			//初始化發送用的DatagramSocket，它包含一個長度為0的字節數組
			outPacket = new DatagramPacket(new byte[0] , 0 ,
				broadcastAddress , BROADCAST_PORT);
			//啟動以本實例的run()方法作為線程體的線程
			new Thread(this).start();
			//創建鍵盤輸入流
			scan = new Scanner(System.in);
			//不斷讀取鍵盤輸入
			while(scan.hasNextLine())
			{
				//將鍵盤輸入的一行字符串轉換字節數組
				byte[] buff = scan.nextLine().getBytes();
				//設置發送用的DatagramPacket里的字節數據
				outPacket.setData(buff);
				//發送數據報
				socket.send(outPacket);
			}
		}
		finally
		{
			socket.close();
		}
	}
	
	public void run()
	{
		try
		{
			while(true)
			{
				//讀取Socket中的數據，讀到的數據放在inPacket所封裝的字節數組里。
				socket.receive(inPacket);
				//打印輸出從socket中讀取的內容
				System.out.println("聊天信息：" + new String(inBuff , 0 , 
					inPacket.getLength()));
			}
		}
		//捕捉異常
		catch (IOException ex)
		{
			ex.printStackTrace();
			try
			{
				if (socket != null)
				{
					//讓該Socket離開該多點IP廣播地址
					socket.leaveGroup(broadcastAddress);
					//關閉該Socket對象
					socket.close();
				}
				System.exit(1);	
			}
			catch (IOException e)
			{
				e.printStackTrace();
			}
		}
	}

	public static void main(String[] args) 
		throws IOException
	{
		new MulticastSocketTest().init();
	}
}