java udp 广播 组播 java发送广播消息

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1. import java.io.IOException;  
2. import java.net.DatagramPacket;  
3. import java.net.DatagramSocket;  
4. import java.net.InetAddress;  
5. import java.net.SocketException;  
6. import java.net.UnknownHostException;  
7. import java.text.SimpleDateFormat;  
8. import java.util.Date;  
9. import java.util.Timer;  
10. public class UdpSend {  
11. public void sendData()throws SocketException,  
12.     UnknownHostException{  
13. new DatagramSocket();// 创建用来发送数据报包的套接字  
14. "hello";  
15. new DatagramPacket(str.getBytes(),  
16.                 str.getBytes().length,  
17. "255.255.255.255"), 3001);  
18. // 构造数据报包，用来将长度为 length 的包发送到指定主机上的指定端口号  
19. try {  
20.             ds.send(dp);  
21. catch (IOException e) {  
22.             e.printStackTrace();  
23.         }  
24.         ds.close();  
25.           
26.     }  
27. public static void main(String[] args) {  
28. new Timer();  
29. new MyTask(), 1000, 1000);  
30.     }  
31. static class MyTask extends java.util.TimerTask{   
32. @Override  
33. public void run() {   
34. new UdpSend();  
35. try {  
36.                     tt.sendData();  
37. catch (SocketException e) {  
38. // TODO Auto-generated catch block  
39.                 e.printStackTrace();  
40. catch (UnknownHostException e) {  
41. // TODO Auto-generated catch block  
42.                 e.printStackTrace();  
43.             }  
44.         }  
45.     }  
46. }