[Java] An example of UDP file transfer

The sender first reads a file locally, reads it in a byte array, and then constructs a DatagramPacket and sends it to the receiver through the DatagramSocket object.
The receiver is stored locally. The two processes are opposite.

Example: transfer a picture. Size: 1525 bytes.

Code:

sender:

import java.io.*;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class SendFile implements Runnable{
    
    
    @Override
    public void run() {
    
    
        send();
    }

    public void send(){
    
    
        try {
    
    
            BufferedInputStream bis = new BufferedInputStream(new FileInputStream("D:\\...\\test.png"));
            int length=bis.available();
            DatagramSocket ds = new DatagramSocket();
            byte[] buf = new byte[length];
            bis.read(buf);
            DatagramPacket dp = new DatagramPacket(buf,buf.length, InetAddress.getByName("127.0.0.1"),10001);
            ds.send(dp);
            ds.close();
			bis.close();
        } catch (IOException e) {
    
    
            e.printStackTrace();
        }
        System.out.println("信息已发送!");
    }
}

receiver:

import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class ReceiveFile implements Runnable{
    
    

    @Override
    public void run() {
    
    
        receive();
    }

    public void receive(){
    
    
        System.out.println("等待信息...");
        try {
    
    
            BufferedOutputStream fos = new BufferedOutputStream(new FileOutputStream(
                    "D:\\...\\testtttt.png"));
            DatagramSocket ds = new DatagramSocket(10001);
            byte[] buf = new byte[1024]; // 小于文件大小
            DatagramPacket dp = new DatagramPacket(buf,buf.length);
            ds.receive(dp);
            ds.close();
            fos.write(dp.getData());
            fos.flush();
            fos.close();
        } catch (IOException e) {
    
    
            e.printStackTrace();
        }

    }
}

Main method:

public class Main {
    
    
    public static void main(String[] args) {
    
    
        new Thread(new ReceiveFile()).start();
        new Thread(new SendFile()).start();
    }
}

The byte array used for receiving is smaller than the size of my file.
The result of this execution is: (the right side is the sent file, the left is the received file)

Change the receiver's code:

byte[] buf = new byte[1024*2]; 

The picture is complete: (the file name is the same, the old picture is directly overwritten)