JAVA基础知识之网络编程——-基于UDP协议的通信例子

UDP是一种不可靠的协议，它在通信两端各建立一个socket，这两个socket不会建立持久的通信连接，只会单方面向对方发送数据，不检查发送结果。

java中基于UDP协议的通信使用DatagramSocket类的receive和send方法即可，但消息需要通过一个特定的类封装（DatagramPacket）

下面是一个基于UDP协议的通信的例子，

服务器端，

 1 package udp;
 2
 3 import java.io.IOException;
 4 import java.net.DatagramPacket;
 5 import java.net.DatagramSocket;
 6
 7 public class Server {
 8     private static final int PORT = 3000;
 9     //数据报大小
10     private static final int  DATA_LEN = 4096;
11     //接受网络数据的字节数组
12     byte[] inBuff = new byte[DATA_LEN];
13     //接收数据
14     private DatagramPacket inPacket = new DatagramPacket(inBuff, inBuff.length);
15     //发送数据
16     private DatagramPacket outPacket;
17     String[] books = new String[]
18     {
19         "疯狂英语",
20         "康熙词典",
21         "TCP协议",
22         "NIO非阻塞channel"
23     };
24     public void init() throws IOException {
25         try {
26             DatagramSocket socket = new DatagramSocket(PORT);
27             for (int i = 0; i < 1000; i++) {
28                 //读取socket中的数据
29                 socket.receive(inPacket);
30                 System.out.println(inBuff == inPacket.getData());
31                 System.out.println(new String(inBuff, 0, inPacket.getLength()));
32
33                 byte[] sendData = books[i % 4].getBytes();
34                 outPacket = new DatagramPacket(sendData, sendData.length, inPacket.getAddress(), PORT);
35                 socket.send(outPacket);
36             }
37         } catch (IOException e) {
38             e.printStackTrace();
39         }
40     }
41
42     public static void main(String[] args) throws IOException {
43         new Server().init();
44     }
45 }

客户端，

 1 package udp;
 2
 3 import java.io.IOException;
 4 import java.net.DatagramPacket;
 5 import java.net.DatagramSocket;
 6 import java.net.InetAddress;
 7 import java.util.Scanner;
 8
 9 public class Client {
10     private static final int PORT = 3000;
11     //数据报大小
12     private static final int  DATA_LEN = 4096;
13     private static final String  DEST_IP = "127.0.0.1";
14     //接受网络数据的字节数组
15     byte[] inBuff = new byte[DATA_LEN];
16     //接收数据
17     private DatagramPacket inPacket = new DatagramPacket(inBuff, inBuff.length);
18     //发送数据
19     private DatagramPacket outPacket;
20
21     public void init() throws IOException {
22         try {
23             //使用随机端口创建socket
24             DatagramSocket socket = new DatagramSocket();
25             outPacket = new DatagramPacket(new byte[0], 0, InetAddress.getByName(DEST_IP), PORT);
26             Scanner scann = new Scanner(System.in);
27             while (scann.hasNextLine()) {
28                 byte[] buff = scann.nextLine().getBytes();
29                 outPacket.setData(buff);
30                 socket.send(outPacket);
31                 socket.receive(inPacket);
32                 System.out.println(new String(inBuff, 0, inPacket.getLength()));
33             }
34         } catch(IOException e) {
35             e.printStackTrace();
36         }
37     }
38
39     public static void main(String[] args) throws IOException {
40         new Client().init();
41     }
42 }

执行结果，启动一个服务器端，再启动一个客户端发一条信息，服务器端输出了信息，