Java udp socket编程

本文仅实现了客户端发送字符串到服务端，服务端将其转换为大写，再发送给服务端

Java 比c++简单明了得多，直接看代码就可以弄懂了。

服务端

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.util.Arrays;

public class Main {
    //服务器
    public static void main(String[] args) {

        // write your code here
        try {
            //众所周知，UDP面向数据报
            DatagramSocket socket = new DatagramSocket(9527);
            byte[] message=new byte[1024];
            while (true){
                DatagramPacket packet = new DatagramPacket(message,1024);
                socket.receive(packet);
                InetAddress address = packet.getAddress();
                int port = packet.getPort();
                byte[] received = packet.getData();
                int len = packet.getLength();
                for(int i=0;i<len;i++){
                    if(received[i]>='a'&&received[i]<='z'){
                        received[i]= (byte) (received[i]-'a'+'A');
                    }
                }

                for(int i=0;i<len;i++){
                    System.out.printf("%c",packet.getData()[i]);
                }
                System.out.println();

                packet.setAddress(address);
                packet.setPort(port);
                socket.send(packet);
            }
        } catch (IOException e) {
            System.out.println("socket有问题");
        }

    }
}

客户端

import java.io.IOException;
import java.net.*;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        // write your code here
        Scanner input = new Scanner(System.in);
        try {
            String words;
            while (true) {
                words=input.next();
                DatagramSocket socket = new DatagramSocket();
                byte[] message = words.getBytes();
                //InetAddress类用来描述一个IP地址
                InetAddress address = InetAddress.getByName("127.0.0.1");
                //DatagramPacket是一个数据报包
                //port用于表述服务器应用进程的端口号
                DatagramPacket packet = new DatagramPacket(message, message.length, address, 9527);
                socket.send(packet);
                System.out.println("发送成功！");
                socket.receive(packet);
                int len = packet.getLength();
                for(int i=0;i<len;i++){
                    System.out.printf("%c",packet.getData()[i]);
                }
                System.out.println();
            }
        } catch (SocketException e) {
            System.out.println("socket有问题");
        } catch (UnknownHostException e) {
            System.out.println("地址有问题");
        }catch (IOException e) {
            System.out.println("发送失败了");
        }
    }
}