Websoket program in java is not responding-CodePudding

I'm practising WebSocket in java and wrote two simple programs which one of them is a server that starts listening in port 9090 and receives a string as input from the client then makes a string uppercase and returns back to the client.

The program has no error but for some reason, it does not work. I can't find out what is the problem.

After debuting it seems like the server doesn't receive the inputs string even though both sides connect to each other successfully. When the user inputs his/her string the client sends it to the server but the server doesn't receive it, therefore, both programs go to the wanting stage and the application will not respond.

could you please help me with the issue? Thanks in advance

server-side code :

    import java.io.*;
    import java.net.ServerSocket;
    import java.net.Socket;
    
    public class Main {
    
        public static void main(String[] args) throws IOException {
        // Start listening at port 9090
            ServerSocket s = new ServerSocket(9090);
            System.out.println("Started: "   s);
            Socket socket = s.accept();
            System.out.println("conecction accepted by "   socket);
    
            try {
                // Buffer reader to get input and save it as "in"
                BufferedReader in = new BufferedReader(
                  new InputStreamReader( 
                         socket.getInputStream() 
                        )
                    );

              // write the output as "out"
                PrintWriter out = new PrintWriter(new BufferedWriter(
                        new OutputStreamWriter(socket.getOutputStream()
                          )
                ));

                // A Loop for waiting to receive the input from the client
                while (true) {
                    System.out.println("Watting for inpute line ...");
                    String line = in.readLine();

                    // print the input string to console to make sure it recive the input
                    System.out.println("inputed Line: "   line);

                    // sent back upper case string to client 
                    out.println(line.toUpperCase());
                    out.flush();
                }
            }finally {
                System.out.println("closing...");
                socket.close();
            }
        }
    }

The cline side code:

import java.io.*;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) throws IOException {
        
    // get the Address for localhost 
        InetAddress addr = InetAddress.getByName(null);
        
     //Connect to the server on pprt 9090   
        Socket s = new Socket(addr,9090);
        
     // read and write to server using buffer reader and printwriter
        try{
            BufferedReader in = new BufferedReader(
                    new InputStreamReader(
                            s.getInputStream()
                    )
            );
            PrintWriter out = new PrintWriter(
                    new BufferedWriter(
                            new OutputStreamWriter(s.getOutputStream())
                    )
            );
       //Get the Ipute string from user 
            Scanner input = new Scanner(System.in);
            while (true){
                System.out.println("Enter your text:");
                String line = input.nextLine();
                if(line.equals("quit"))
                    break;
                
        // Sent the input string to the server using 'out'          
                out.println(line);
        // Recive the upper case string from server        
                String response = in.readLine();
                System.out.println("Echo:... "   response);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            System.out.println("closing...");
            s.close();
        }
    }
}

CodePudding user response：

The server side is waiting to read a line from the client, it should work if you flush the PrintWriter on the client side:

// Sent the input string to the server using 'out'          
out.println(line);
out.flush();