public class MainActivity extends Activity { 
 /*发送广播端的socket*/ 
 private MulticastSocket ms; 
 /*发送广播的按钮*/ 
 private Button sendUDPBrocast; 
 @Override 
 public void onCreate(Bundle savedInstanceState) { 
  super.onCreate(savedInstanceState); 
  init(); 
 } 
 /*初始化参数*/ 
 public void init() { 
  setContentView(R.layout.main); 
  sendUDPBrocast = (Button) findViewById(R.id.send); 
  sendUDPBrocast.setOnClickListener(new SendUDPBrocastListener()); 
  try { 
   /*创建socket实例*/ 
   ms = new MulticastSocket(); 
  } catch (Exception e) { 
   e.printStackTrace(); 
  } 
 } 
 /** 
  * 单击按钮时，发送局域网广播 
  * */ 
 class SendUDPBrocastListener implements OnClickListener{ 
  @Override 
  public void onClick(View v) { 
   //发送的数据包，局网内的所有地址都可以收到该数据包 
   DatagramPacket dataPacket = null; 
   try { 
    ms.setTimeToLive(4); 
    //将本机的IP（这里可以写动态获取的IP）地址放到数据包里，其实server端接收到数据包后也能获取到发包方的IP的 
    byte[] data = "192.168.1.101".getBytes(); 
    //224.0.0.1为广播地址 
    InetAddress address = InetAddress.getByName("224.0.0.1"); 
    //这个地方可以输出判断该地址是不是广播类型的地址 
    System.out.println(address.isMulticastAddress()); 
    dataPacket = new DatagramPacket(data, data.length, address, 
      8003); 
    ms.send(dataPacket); 
    ms.close(); 
   } catch (Exception e) { 
    e.printStackTrace(); 
   } 
  } 
 } 
} 

public class MainActivity extends Activity implements Runnable { 
 private MulticastSocket ds; 
 String multicastHost="224.0.0.1"; 
 InetAddress receiveAddress; 
 @Override 
 public void onCreate(Bundle savedInstanceState) { 
  super.onCreate(savedInstanceState); 
  setContentView(R.layout.main); 
  try { 
   ds = new MulticastSocket(8003); 
   receiveAddress=InetAddress.getByName(multicastHost); 
   ds.joinGroup(receiveAddress); 
   new Thread(this).start(); 
  } catch (Exception e1) { 
   // TODO Auto-generated catch block 
   e1.printStackTrace(); 
  } 
 } 
 @Override 
 public void run() { 
  // TODO Auto-generated method stub 
  byte buf[] = new byte[1024]; 
  DatagramPacket dp = new DatagramPacket(buf, 1024); 
  while (true) { 
   try { 
    ds.receive(dp); 
    //Toast.makeText(this, new String(buf, 0, dp.getLength()), Toast.LENGTH_LONG); 
    System.out.println("client ip : "+new String(buf, 0, dp.getLength())); 
   } catch (Exception e) { 
    e.printStackTrace(); 
   } 
  } 
 } 
}