Java中使用UDP协议的Socket通信

Java中使用UDP协议的Socket通信：

基本测试代码：
客户端：

package udpsocket;

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

public class Demo1_Send {
    public static void main(String[] args) throws Exception {

        // 在发生数据之前，你得先把数据准备好，发生目标的IP地址，端口

        // 准备一个字符串数据，待发送
        String sendMsg = "你在做什么呢？";

        // 获取目标主机的IP地址
        InetAddress hostIP = InetAddress.getByName("127.0.0.1");
        // 获取目标主机的端口号
        int hostPort = 6666;

        // 创建DatagramSocket对象，相当于创建码头
        DatagramSocket socket = new DatagramSocket();

        // 创建DatagramPacket对象，相当于创建船只，参数为：发数据的字节码，字节码的长度，目标IP地址，目标端口号
        DatagramPacket packet = new DatagramPacket(sendMsg.getBytes(), sendMsg.getBytes().length, hostIP, hostPort);

        // 开始发送数据，在码头护送包装数据的船只
        socket.send(packet);

        // 发送完毕后将socket关闭，码头关门
        socket.close();
    }
}

服务器端：

package udpsocket;

import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class Demo1_Receive {
    public static void main(String[] args) throws Exception {

        // 创建DatagramSocket对象，并指定端口号
        DatagramSocket socket = new DatagramSocket(6666);

        // 创建DatagramPacket对象，并指定接收容器，及其长度
        DatagramPacket packet = new DatagramPacket(new byte[1024], 1024);

        // 开始接收数据
        socket.receive(packet);

        // 取出数据
        byte[] msgArr = packet.getData();
        // 获取有效数据的长度
        int length = packet.getLength();

        // 将字节码还原成字符串
        String msgStr = new String(msgArr, 0, length);
        System.out.println(msgStr);
    }
}

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改进后的代码：

客户端：

package udpsocket;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.Scanner;

public class Demo2_Send {
    public static void main(String[] args) throws Exception {

        Scanner sc = new Scanner(System.in);

        DatagramSocket socket = new DatagramSocket();

        InetAddress hostIP = InetAddress.getByName("127.0.0.1");
        int hostPort = 7777;

        System.out.println("请输入发送信息，输入over结束：");
        while (sc.hasNext()) {
            String msgStr = sc.nextLine();
            if ("over".equals(msgStr))  break;

            DatagramPacket packet = new DatagramPacket(msgStr.getBytes(), msgStr.getBytes().length, hostIP, hostPort);
            socket.send(packet);
        }

        socket.close();
    }
}

服务器端：

package udpsocket;

import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class Demo2_Receive {
    public static void main(String[] args) throws Exception {

        DatagramSocket socket = new DatagramSocket(7777);

        while (true) {
            DatagramPacket packet = new DatagramPacket(new byte[1024], 1024);
            socket.receive(packet);

            // 取出数据
            byte[] msgArr = packet.getData();
            int length = packet.getLength();
            String msgStr = new String(msgArr, 0, length);

            // 获取发送者的IP地址，端口号
            String srcIP = packet.getAddress().getHostAddress();
            int srcPort = packet.getPort();

            System.out.println(srcIP + "-" + srcPort + "：" + msgStr);
        }
    }
}