Use UDP to send data in one direction

It is best to run the receiver's .java file first, and then run the sender's. So as not to cause data loss because the receiver has not started to receive data, the sender will send it first

sender

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

/*
* UDP传输的发送端：
1 建立udp的socket对象
2.将要发送的数据封装成数据包
3.通过udp的socket对象,将数据包发送出
4.释放资源
* */
public class SendData {//这里只实现单方向传数据A->B

    public static void main(String[] args) throws IOException {
        //建立udp的socket对象,并指定本主机要用哪个端口（1-65535）发送数据
        DatagramSocket socket = new DatagramSocket(69);

        //用键盘循环输入要发送的内容
        BufferedReader bufferin = new BufferedReader(new InputStreamReader(System.in));
        String s;
        while ((s = bufferin.readLine()) != null) {
            byte[] bytes = s.getBytes();//把字符串->字节
            //在给定主机名的情况下，返回其IP地址的对应对象
            InetAddress targerIP = InetAddress.getByName("127.0.0.1");//目的IP
            //将要发送的数据封装成数据包,目的端口8888
            DatagramPacket packet = new DatagramPacket(bytes, 0, bytes.length, targerIP, 8888);
            //再把数据报输到socke的send方法里，发送出去,
            socket.send(packet);
            if (s.equals("886")) {//发送方发送886，说明数据发送完毕，接收方也可以停止接收
                break;
            }
        }
        socket.close();
    }
}

receiver

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketAddress;

/*
* 1.建立udp的socket对象.
2.创建用于接收数据的数据报包，通过socket对象的receive方法接收数据
3.通过数据包对象的功能来完成对接收到数据进行解析.
4.可以对资源进行释放
* */
public class ReceiveData {
    public static void main(String[] args) throws IOException {
        //建立udp的socket对象,输入本主机用来接收数据的端口
        DatagramSocket socket = new DatagramSocket(8888);
        // 创建充当缓冲区的字节数组
        byte[] bytes = new byte[1024];
        //让数据报包的缓冲区指针指向bytes
        DatagramPacket receivePacket = new DatagramPacket(bytes, 0, bytes.length);
        //接收数据，送到缓冲区
        while (true) {
            socket.receive(receivePacket);//receive是阻塞方法，在接收到数据报前一直阻塞
            // 解析数据报包
            byte[] data = receivePacket.getData();//得到缓冲区所有数据，相当于data=bytes
            int length = receivePacket.getLength();//返回缓冲区发送或接收到的数据长度
            int offset = receivePacket.getOffset();//返回缓冲区发送或接收到的数据偏移量
            String s = new String(data, offset, length);
            //另解，直接用bytes打印结果
            // String s = new String(bytes, 0, bytes.length);bytes的有效数据长度应该换成上面的length
            System.out.println(s);

            //从数据报包里获取源ip和源端口，如果是在发送方获得目的IP和目的端口号
           /* 方式1
            InetAddress sourceIP = receivePacket.getAddress();
            int port = receivePacket.getPort();
            System.out.println("接收到了来自"+ sourceIP +"/" + port +":"+s);
            方式2 获得IP+端口
            SocketAddress socketAddress = receivePacket.getSocketAddress();
            System.out.println("接受到了来自" + socketAddress + ":" + s);
            */

            if (s.equals("886")) {//如果发送方发送886，接收停止
                break;
            }
        }
        //关闭资源
        socket.close();
    }
}