Java Socket编程(四)Socket进阶
2012-08-06 21:10 java线程例子 阅读(373) 评论(0) 编辑 收藏 举报
一、多播与广播
我们可以向每个接受者单播一个数据副本,但这样做效率可能非常低。
只有UDP套接字允许广播和多播,两者的区别是:广播会发送到网络上所有可达的
主机,有些操作系统可能不允许普通用户进行广播操作;而多播只发送给感兴趣的
主机。具体来说是调用MulticastSocket的joinGroup()加入到多播组的主机。
public class MulticastReceiverTest { public static void main(String[] args) throws Exception { final InetAddress address = InetAddress.getByName("224.1.1.1"); final int port = 45599; for (int i = 0; i < 5; i++) { new Thread("Thread #" + i){ @Override public void run() { try { MulticastSocket sock = new MulticastSocket(port); sock.joinGroup(address); byte[] msg = new byte[256]; DatagramPacket packet = new DatagramPacket(msg, msg.length); sock.receive(packet); System.out.println(Thread.currentThread().getName() + " receive: " + new String(packet.getData())); } catch (IOException e) { e.printStackTrace(); } } }.start(); } Thread.sleep(2000); MulticastSocket sock = new MulticastSocket(); sock.setTimeToLive(32); byte[] msg = "hellomulticast".getBytes(); DatagramPacket packet = new DatagramPacket(msg, msg.length, address, port); sock.send(packet); System.out.println("Message sent"); } }