Knock Knock application with server and UI

Question

I am creating a simple Knock Knock application (socket programming) where there is a localhost server and there is a client.the program is simple, the server will tell the k

Answer 1

Where exactly are you printing to the textarea as you are saying the while loop simply gets the text and prints it to the console.

// Put this code somewhere in the Client class so that when it receives something,
// it can be added to the `JTextArea`
while ((fromServer = in.readLine()) != null) 
{
    // You seems like missed the part that sends it to the textArea
    System.out.println("Server: " + fromServer);
    // Here send the received thing to your textarea, which goes something like this
    String str = "Server : " + fromServer + "\n";
    tarea.append(str);

    if (fromServer.equals("Bye."))
        break;

    // You can remove this part and put it inside the textField's actionPerformed method. 
    fromUser = stdIn.readLine();
    if (fromUser != null) 
    {
        System.out.println("Client: " + fromUser);
        out.println(fromUser);
    }
}

BRAND NEW EDIT :

Just start your KnockKnockServer from the command prompt, not from your class that extends JFrame. Just simply write java KnockKnockServer, to run your server on the command prompt, now on the new command prompt compile this class i am giving you and run it too like java KnockKnockClient, you will get an idea it's not working fully though.

import java.awt.BorderLayout;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import javax.swing.*;


public class KnockKnockClient extends JFrame
{

    public String fromServer;
    public String fromUser;
    // Added by me.--------------------
    private JTextArea tarea;
    private JTextField tfield;
    private JScrollPane spane;
    private PrintWriter out = null;
    /*------------------------------------*/

    public void Client() throws IOException 
    {
        Socket kkSocket = null;
        //PrintWriter out = null;  Shifted this to the instance variable
        BufferedReader in = null;

        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
        try {
            kkSocket = new Socket("127.0.0.1", 4444);
            out = new PrintWriter(kkSocket.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(kkSocket.getInputStream()));
        } catch (UnknownHostException e) {
            System.err.println("Don't know about host: 127.0.0.1");
            System.exit(1);
        } catch (IOException e) {
            System.err.println("Couldn't get I/O for the connection to: 127.0.0.1");
            System.exit(1);
        }

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);

        JPanel contentPane = new JPanel();

        tarea = new JTextArea(10, 10);
        spane = new JScrollPane(tarea);
        tarea.setLineWrap(true);
        tfield = new JTextField(10);

        tfield.requestFocusInWindow();

        contentPane.setLayout(new BorderLayout());
        contentPane.add(spane, BorderLayout.CENTER);
        contentPane.add(tfield, BorderLayout.PAGE_END);

        setContentPane(contentPane);
        pack();
        setVisible(true); 

        Thread receiveMessage = new Thread(new ReceiveChat(in, stdIn, out));    
        receiveMessage.start();



        tfield.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                // Here you will send it to the server side too, put that code here
                fromUser = tfield.getText() + "\n";
                if (fromUser != null) 
                {
                    System.out.println("Client: " + fromUser);
                    tarea.append(fromUser);
                    out.println(fromUser);
                    tfield.setText("");
                }
            }
        });
        //out.close();
        //in.close();
        //stdIn.close();
        //kkSocket.close();
     }    

     private class ReceiveChat implements Runnable
     {
        private BufferedReader in;
        private BufferedReader stdIn;
        private PrintWriter out;

        public ReceiveChat(BufferedReader in, BufferedReader stdIn, PrintWriter out)
        {
            this.in = in;
            this.stdIn = stdIn;
            this.out = out;
        }

        public void run()
        {
            try
            {
                while ((fromServer = in.readLine()) != null) {
                //System.out.println("Server: " + fromServer);
                String str = "Server : " + fromServer + "\n";
                tarea.append(str);
                tarea.setCaretPosition(tarea.getDocument().getLength());

                if (fromServer.equals("Bye."))
                    break;
                /*Commented out by me.*/
                /*fromUser = stdIn.readLine();
                if (fromUser != null) {
                    System.out.println("Client: " + fromUser);
                    out.println(fromUser);
                }   */
                }
            }
            catch(Exception e)
            {
                e.printStackTrace();
            }
        }
     }

    public static void main(String... args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                KnockKnockClient client = new KnockKnockClient();
                try
                {
                    client.Client();
                }
                catch(Exception e)
                {
                    e.printStackTrace();
                }
            }
        });
    }
}

Just let the while loop of your KnockKnockServer class look like this :

while ((inputLine = in.readLine()) != null) 
{
    if (inputLine.length() > 0)
    {
        outputLine = kkp.processInput(inputLine);            
        out.println(outputLine);
        if (outputLine.equals("Bye."))
            break;
    }   
}

This will make it work as expected.