Simple understanding of Socket

Socket communication principle

• The input stream of Server server is equivalent to the output stream of Client
• The output stream of Server server is equivalent to the input stream of Client

Be careful

• File transfer uses byte stream
  
• Using DataOutputStream, DataOutputStream can pass java basic types and streams

Code

Server.java

package csmode2;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * @author StarsOne
 * @date Create in  2019-4-14 0014 10:53:58
 * @description
 */
class Server {
    public static void main(String[] args) {
        try (ServerSocket serverSocket = new ServerSocket(9090)){

            System.out.println("Server started...");
            
            while (true) {
                System.out.println("Waiting to receive file");
                //After the accept method is called, it is always waiting for the file to be accepted
                Socket socket = serverSocket.accept();//Receive data from client
                //To the background thread
                new AcceptThread(socket.getInputStream()).start();
            }


        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

AcceptThread.java

package csmode2;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * @author StarsOne
 * @date Create in  2019/4/15 0015 14:17
 * @description
 */
class AcceptThread extends Thread {
    private InputStream inputStream;

    public AcceptThread(InputStream inputStream) {
        this.inputStream = inputStream;
    }

    @Override
    public void run() {
        try {
            //Wrapping the input stream with DataInputStream
            DataInputStream dataInputStream = new DataInputStream(inputStream);

            String fileName = dataInputStream.readUTF();
            System.out.println(fileName);//Display the filename in the console

            //Write files to a location
            FileOutputStream fileOutputStream = new FileOutputStream("Q:\\MY" + File.separator + fileName);
            int c = -1;
            while ((c = dataInputStream.read()) != -1) {
                fileOutputStream.write(c);
                fileOutputStream.flush();
            }

            System.out.println("File upload succeeded!");

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Client.java

package csmode2;

import java.io.*;
import java.net.Socket;

/**
 * @author StarsOne
 * @date Create in  2019-4-14 0014 10:53:49
 * @description
 */
class Client {
    public static void main(String[] args) {
        //        File[] files = new File("E:\\wan\\testfile").listFiles();
        //If there are multiple files, just put them into a list or array, and use the for loop to upload all the files of the array to the server

        //Uploaded files
        File file = new File("R:\\Cartoon pictures\\test.jpg");

        try(Socket socket = new Socket("localhost", 9090)) {

            OutputStream outputStream = socket.getOutputStream();
            //Using DataOutputStream
            DataOutputStream dataOutputStream = new DataOutputStream(outputStream);
            //File name to server
            dataOutputStream.writeUTF(file.getName());
            dataOutputStream.flush();//Refresh stream, transfer to server

            //File transfer to server through byte stream
            //Byte stream read hard disk file first
            BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream(file));
            
            int c = -1;
            while ((c=bufferedInputStream.read())!=-1) {
                //Write the read file to DataOutputStream in bytes, and then transfer it to the server
                //Here you can also use byte [] data for reading and writing
                dataOutputStream.write(c);
                dataOutputStream.flush();
            }

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}