Java网络编程之UDP网络通信详解

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;


public class UDPReceiverA {
    public static void main(String[] args) throws IOException {
        //1.创建一个DatagramSocket对象，准备在9999接收数据
        DatagramSocket socket = new DatagramSocket(9999);
        //2.构建一个DatagramPacket对象，准备接收数据
        byte[] buf = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buf, buf.length);
        //3.调用接收方法,将通过网络传输的 DatagramPacket对象 填充到 packet对象
        System.out.println("接收端A 等待接收数据...");
        socket.receive(packet);
        //4.把packet进行拆包，取出数据
        int length = packet.getLength();//实际数据字节长度
        byte[] data = packet.getData();//实际接收的数据
        String s = new String(data, 0, length);
        System.out.println(s);

        //回复信息给B端
        data = "你好！发送端".getBytes();
        packet = new DatagramPacket(data, 0, data.length,
                InetAddress.getLocalHost(), 9998);
        socket.send(packet);
        //5.关闭资源
        socket.close();
    }
}

import java.io.IOException;
import java.net.*;


public class UDPSenderB {
    public static void main(String[] args) throws IOException {
        //1.创建 DatagramSocket 对象，准备在9998发送和接收数据
        DatagramSocket socket = new DatagramSocket(9998);
        //2.将需要发送的数据，封装到 DatagramPacket 中
        byte[] data = "你好！接收端".getBytes();
        DatagramPacket datagramPacket =
                new DatagramPacket(data, 0, data.length,
                        InetAddress.getLocalHost(), 9999);
        socket.send(datagramPacket);

        //接收A消息
        socket.receive(datagramPacket);
        int length = datagramPacket.getLength();//实际数据字节长度
        data = datagramPacket.getData();//实际接收的数据
        String s = new String(data, 0, length);
        System.out.println(s);
        //关闭资源
        socket.close();
    }
}