网络编程 UDP

不用连接，需要指定对方地址！

UDP是没有客户端和服务端的概念。

★ UDP消息发送

1.创建一个发送端  UdpClientDemo01.java

package com.ckfuture;

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

public class UdpClientDemo01 {
    public static void main(String[] args) throws Exception {
        //1.建立一个Socket
        DatagramSocket socket = new DatagramSocket();
        //2.建立个包
        String msg="你好啊，服务器！";
        //发送给谁
        InetAddress IP = InetAddress.getByName("127.0.0.1");
        int port=9090;
        //数据，数据的起始，数据的长度，要发给谁
        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, IP, port);

        //3.发送包
        socket.send(packet);

        //关闭资源
        socket.close();
    }
}

2.创建一个接收端  UdpServerDemo01.java

package com.ckfuture;

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

public class UdpServerDemo01 {
    public static void main(String[] args) throws Exception {
        //1.开放端口
        DatagramSocket socket = new DatagramSocket(9090);
        //2.接收数据包
        byte[] buffer = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);

        socket.receive(packet);
        System.out.println(packet.getAddress().getHostAddress());
        System.out.println(new String(packet.getData(),0,packet.getLength()));

        //关闭资源
        socket.close();
    }
}

3.依次运行接收端和发送端

 

 ★ UDP聊天实现（单线程）

1.创建一个消息发送类  UdpSenderDemo01.java

package com.ckfuture;

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

public class UdpSenderDemo01 {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(8888);

        //准备数据
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        while(true){
            String data = reader.readLine();
            byte[] datas = data.getBytes();
            DatagramPacket packet = new DatagramPacket(datas,0,datas.length,new InetSocketAddress("localhost",6666));
            socket.send(packet);
            //本地退出
            if(data.equals("bye")){
                break;
            }
        }
        //关闭资源
        socket.close();
    }
}

2.创建一个接收消息类  UdpReceiveDemo01.java

package com.ckfuture;

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

public class UdpReceiveDemo01 {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(6666);

        //死循环接收信息
        while(true){
            //准备接受消息
            byte[] container = new byte[1024];
            DatagramPacket packet = new DatagramPacket(container,0,container.length);
            socket.receive(packet);//阻塞式接收消息

            //转换成字符串
            byte[] data = packet.getData();
            String receiveData = new String(data, 0, data.length);
            //输出接收的消息
            System.out.println(receiveData);

            //断开连接
            if(receiveData.equals("bye")){
                break;
            }
        }
        socket.close();

    }
}

3.依次运行发送端和接收端

只是实现了一个循环发送一个循环接收，并没有实现双方聊天的效果。

 

 

 

 ★多线程

1.建立一个发送类  TalkSend.java

package com.ckfuture;

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

public class TalkSend implements Runnable {

    DatagramSocket socket=null;
    BufferedReader reader=null;
    private int  fromPort;//自己的端口
    private String toIP;//对方IP地址
    private int toPort;//对方端口号


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

        try{
             socket = new DatagramSocket(fromPort);
             reader=new BufferedReader(new InputStreamReader(System.in));
        }catch (Exception e){
            e.printStackTrace();
        }

    }

    @Override
    public void run() {
        while(true){
            try{
                String data=reader.readLine();
                byte[] datas = data.getBytes();
                DatagramPacket packet = new DatagramPacket(datas, 0, datas.length, new InetSocketAddress(this.toIP, this.toPort));
                socket.send(packet);
                if (data.equals("bye")){
                    break;
                }
            }catch (Exception e){
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

2.创建一个接收类  TalkReceive.java

package com.ckfuture;

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

public class TalkReceive implements  Runnable{

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

    public TalkReceive(int port,String msgFrom) {
        this.port = port;
        this.msgFrom=msgFrom;
        try {
            socket = new DatagramSocket(port);
        } catch (SocketException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void run() {

        while (true){

            try {
                //准备接收数据
                byte[] container = new byte[1024];
                DatagramPacket packet = new DatagramPacket(container, 0, container.length);
                socket.receive(packet);//阻塞式接收信息

                //断开连接
                byte[] data = packet.getData();
                String receiveData = new String(data, 0, data.length);
                System.out.println(msgFrom+":"+receiveData);
                if(receiveData.equals("bye")){
                    break;
                }
            } catch (IOException e) {
                e.printStackTrace();
            }

        }
        socket.close();
    }
}

3.创建一个 测试端  TalkStudent.java

package com.ckfuture;

public class TalkStudent {
    public static void main(String[] args) {

        new Thread(new TalkSend(7777,"localhost",9999)).start();

        new Thread(new TalkReceive(8888,"teacher say")).start();
    }
}

4.创建另一个测试端 TalkTeacher.java

package com.ckfuture;

public class TalkTeacher {
    public static void main(String[] args) {
        new Thread(new TalkSend(5555,"localhost",8888)).start();
        new Thread(new TalkReceive(9999,"学生")).start();
    }
}