通過DatagramSocket類來實現。此類表示用來發送和接收數據報包的套接字。

發送端代碼如下:

 2 
 3 import java.io.IOException;
 4 import java.net.*;
 5 import java.util.Scanner;
 6 
 7 public class Send implements Runnable{
 8     @Override
 9     public void run() {
10         //創建一個發送消息的套接字
11         DatagramSocket sendSocket = null;
12         try
 
 {
13             sendSocket = new DatagramSocket();
14         } catch (SocketException e) {
15             e.printStackTrace();
16         }
17         while (true) {
18             try {
19                 System.out.println("發送端發送消息");
20                 Scanner sc = new Scanner(System.in);
21                 String msg = sc.next();
 
22 
23                 byte [] bytes = msg.getBytes();//發送的內容轉化為字節數組
24                 InetAddress ip = InetAddress.getByName("192.168.31.169");//接受內容的Ip地址
25 
26                 //創建要發送的數據包，然後用套接字發送
27                 DatagramPacket datagramPacket = new DatagramPacket(bytes,bytes.length,ip,8080);
28                 //
 
用套接字發送數據包
29                 sendSocket.send(datagramPacket);
30 
31             } catch (SocketException e) {
32                 e.printStackTrace();
33             } catch (UnknownHostException e) {
34                 e.printStackTrace();
35             } catch (IOException e) {
36                 e.printStackTrace();
37             }
38         }
39     }
40 
41     public static void main(String[] args){
42         Send s = new Send();
43         Thread thread = new Thread(s);
44         thread.start();
45     }
46 }

接收端代碼如下：

 2 
 3 import java.io.IOException;
 4 import java.net.DatagramPacket;
 5 import java.net.DatagramSocket;
 6 import java.net.InetAddress;
 7 import java.net.SocketException;
 8 
 9 public class Receive implements Runnable {
10     @Override
11     public void run() {
12         System.out.println("接收端");
13         //創建接受消息的套接字
14         DatagramSocket receviceSocket = null;
15         try {
16             receviceSocket = new DatagramSocket(8080);
17         } catch (SocketException e) {
18             e.printStackTrace();
19         }
20         while (true) {
21             try {
22                 byte [] bytes = new byte[2048];
23                 //創建一個數據包來接受消息
24                 DatagramPacket datagramPacket = new DatagramPacket(bytes,bytes.length);
25                 //用套接字接受數據包
26                 receviceSocket.receive(datagramPacket);
27                 //得到發送端的ip地址
28                 InetAddress ip = datagramPacket.getAddress();
29                 //將接受到的消息轉換為字符串
30                 String rec = new String(datagramPacket.getData()) ;
31                 System.out.println(ip.getHostAddress()+"發送的消息為："+rec);
32 
33             } catch (SocketException e) {
34                 e.printStackTrace();
35             } catch (IOException e) {
36                 e.printStackTrace();
37             }
38         }
39     }
40 
41     public static void main(String[] args) {
42         Receive r = new Receive();
43         Thread thread = new Thread(r);
44         thread.start();
45     }
46 }

因為要一直接受消息和發送消息，故用了while循環。

註意事項：發送端的端口要和接收端的端口保持一致。　　

這裏我接受消息的ip地址設置為自己的ip地址來演示實際效果。

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