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????3

??UDP????

UDP?????????????????????????????????????????????????????????UDP??????

• ???
  • ?????TCP???UDP??????????????????
  • ???????????????????????????????
• ???
  • ????????????
  • ?????????????????????????
• ???
  • ???????????????????????
  • ??????????????????

????UDP?????????

?Java??????UDP??????????java.net???DatagramPacket????????????

1. ?????DatagramPacket

DatagramPacket?????????????????

• ?????
  • DatagramPacket(byte[] buf, int length)??????length?????
  • DatagramPacket(byte[] buf, int length, InetAddress address, int port)???????????????
• ?????
  • void send(DatagramPacket p)????????
  • void receive(DatagramPacket p)????????
  • void close()??????????

2. ??????DatagramSocket

DatagramSocket????????????????????

• DatagramSocket()????????????????
• DatagramSocket(int port)?????????
• close()??????????

??????

?????UDP???Java?????

1. ???UDP???

package com.wangxing.test1;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Scanner;
public class UDPClient {
    public static void main(String[] args) throws Exception {
        Scanner input = new Scanner(System.in);
        System.out.println("???????????");
        String info = input.nextLine();
        
        byte[] sbyte = info.getBytes();
        DatagramPacket sPacket = new DatagramPacket(sbyte, sbyte.length, InetAddress.getLocalHost(), 3000);
        
        DatagramSocket client = new DatagramSocket();
        client.send(sPacket);
        client.close();
    }
}

2. ???UDP???

package com.wangxing.test1;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
public class UDPServer {
    public static void main(String[] args) throws Exception {
        byte[] buf = new byte[1024];
        DatagramPacket sPacket = new DatagramPacket(buf, buf.length);
        
        DatagramSocket server = new DatagramSocket(3000);
        server.receive(sPacket);
        
        byte[] data = sPacket.getData();
        int len = sPacket.getLength();
        String info = new String(data, 0, len);
        System.out.println("????????" + sPacket.getAddress().getHostAddress() + ":" + sPacket.getPort() + "????????" + info);
        
        server.close();
    }
}

3. ???UDP???????

package com.wangxing.test4;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.util.Scanner;
public class UDPClient4 {
    public static void main(String[] args) throws Exception {
        Scanner input = new Scanner(System.in);
        DatagramSocket server = new DatagramSocket();
        byte[] sbyte = new byte[1024];
        DatagramPacket spack = new DatagramPacket(sbyte, sbyte.length);
        
        boolean flag = true;
        while (flag) {
            System.out.println("??????????");
            String info = input.nextLine();
            
            byte[] fbyte = info.getBytes();
            DatagramPacket fpack = new DatagramPacket(fbyte, fbyte.length, InetAddress.getLocalHost(), 3000);
            server.send(fpack);
            
            if (info.equals("886")) {
                flag = false;
                System.out.println("??????");
            } else {
                server.receive(spack);
                byte data[] = spack.getData();
                int len = spack.getLength();
                String msg = new String(data, 0, len);
                System.out.println("?????????????" + msg);
            }
        }
        try {
            server.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println("??????");
    }
}
// ??????
class ClientThread4 extends Thread {
    private DatagramSocket server;
    private DatagramPacket datagramPacket;
    private boolean falg = true;
    public ClientThread4(DatagramSocket server, DatagramPacket datagramPacket) {
        this.server = server;
        this.datagramPacket = datagramPacket;
    }
    @Override
    public void run() {
        try {
            while (falg) {
                byte data[] = datagramPacket.getData();
                int len = datagramPacket.getLength();
                String info = new String(data, 0, len);
                System.out.println("???????????" + info);
                if (info.equals("886")) {
                    falg = false;
                    System.out.println("?????");
                } else {
                    info = "server?" + info;
                    byte fbyte[] = info.getBytes();
                    DatagramPacket fPacket = new DatagramPacket(fbyte, fbyte.length, datagramPacket.getAddress(), datagramPacket.getPort());
                    server.send(fPacket);
                    System.out.println("??????");
                    falg = false;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

?????UDP?????

package com.wangxing.test4;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
public class UDPServer4 {
    public static void main(String[] args) throws Exception {
        DatagramSocket server = new DatagramSocket(3000);
        byte[] bytes = new byte[1024];
        while (true) {
            DatagramPacket packet = new DatagramPacket(bytes, bytes.length);
            System.out.println("****??????????????????");
            server.receive(packet);
            ClientThread4 clientThread4 = new ClientThread4(server, packet);
            clientThread4.setPriority(4);
            clientThread4.start();
        }
    }
}

???????????UDP???Java??????????????????????????????????