网络编程

6 UDP

6.2.2 UDP聊天实现

“循环实现消息的发送和接收”

接收端只能接收到消息而无法反馈交流

接收：

package com.duo.chat;

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

public class UdpReceiveDemo1 {

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

        DatagramSocket datagramSocket = new DatagramSocket(6666);

        while (true) {
            //准备包裹：用于接收数据
            byte[] container = new byte[1024];
            DatagramPacket datagramPacket = new DatagramPacket(container, 0,
                    container.length);
            datagramSocket.receive(datagramPacket);  //阻塞式接收包裹

            //断开连接
            byte[] bytes = datagramPacket.getData();
            String data = new String(bytes, 0, bytes.length);
            System.out.println(data);

            if (data.equals("bye")) {
                break;
            }
        }

        datagramSocket.close();
    }
}

发送：

package com.duo.chat;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;

public class UdpSendDemo1 {

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

        DatagramSocket datagramSocket = new DatagramSocket(8888);

        //准备数据：控制台读取 System.in
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));

        while (true) {
            String data = bufferedReader.readLine();
            byte[] bytes = data.getBytes();
            DatagramPacket datagramPacket = new DatagramPacket(bytes, 0,
                    bytes.length, new InetSocketAddress("localhost", 6666));

            datagramSocket.send(datagramPacket);
            if (data.equals("bye")) {
                break;
            }
        }

        datagramSocket.close();
    }
}

运行结果：

如上所示，可以在控制台中多次输入消息发送，接收方成功收到消息。在输入“bye”时，连接断开。

6.2.3 多线程在线咨询

将上述消息发送端和接收端代码实现多线程在线咨询

互相沟通交流（即双方都可以是发送方，也可以是接收方）

发送端：

package com.duo.chat;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import java.net.SocketException;

public class Send implements Runnable {

    DatagramSocket datagramSocket = null;
    BufferedReader bufferedReader = null;
    private int fromPort;
    private String toIP;
    private int toPort;

    public Send(int fromPort, String toIP, int toPort) {
        this.fromPort = fromPort;
        this.toIP = toIP;
        this.toPort = toPort;

        try {
            datagramSocket = new DatagramSocket(fromPort);
            bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        } catch (SocketException e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public void run() {
        while (true) {
            try {
                String data = bufferedReader.readLine();
                byte[] bytes = data.getBytes();
                DatagramPacket datagramPacket = new DatagramPacket(bytes, 0,
                        bytes.length, new InetSocketAddress(this.toIP, this.toPort));

                datagramSocket.send(datagramPacket);
                if (data.equals("bye")) {
                    break;
                }
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        datagramSocket.close();
    }
}

接收端：

package com.duo.chat;

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

public class Receive implements Runnable {

    DatagramSocket datagramSocket = null;
    private int port;
    private String msgFrom;

    public Receive(int port, String msgFrom) {
        this.port = port;
        this.msgFrom = msgFrom;
        try {
            datagramSocket = new DatagramSocket(port);
        } catch (SocketException e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public void run() {

        while (true) {
            try {
                //准备包裹：用于接收数据
                byte[] container = new byte[1024];
                DatagramPacket datagramPacket = new DatagramPacket(container, 0,
                        container.length);
                datagramSocket.receive(datagramPacket);  //阻塞式接收包裹

                //断开连接
                byte[] bytes = datagramPacket.getData();
                String data = new String(bytes, 0, bytes.length);

                System.out.println(msgFrom + ": " + data);

                if (data.equals("bye")) {
                    break;
                }
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }

        datagramSocket.close();
    }
}

然后写两个模拟在线咨询的对象：

老师：

package com.duo.chat;

public class Teacher {

    public static void main(String[] args) {
        new Thread(new Send(3333, "localhost", 4444)).start();
        new Thread(new Receive(2222, "学生")).start();
    }
}

学生：

package com.duo.chat;

public class Stundent {

    public static void main(String[] args) {
        new Thread(new Send(1111, "localhost", 2222)).start();
        new Thread(new Receive(4444, "老师")).start();
    }
}

运行结果：

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