Why is this happening?

Question

I am trying to create a remote-desktop monitor application using java where a server can see the screenshot of the client and also can monitor the number of processes running on the client. Here is the screenshot of the user interface

But now I have a bug which I can't fix. I have debugged it several times but I couldn't find a way to track the bug. Here are the problems which I am facing right now:=

1) When I press the "GET PROCESS LIST" button nothing happens. The process list is fetched to the textarea when the capture button is pressed i.e First I have to press the "GET PROCESS LIST" then I have to press the capture button for the list of processes to show up.

2) When I press the capture button it only captures the screenshot of the client once. After that when I press the capture button it doesn't do anything. Same is with the Get Process Button. They only get executed once.

I have tried debugging both the client and the server but failed to track the bug.

Here is my code for client and server. The code for server is big but I have to provide the whole code as because I don't know where the problem actually lies.

This is the client

public class ScreenClient {

    private static BufferedImage screen;


    public static void main(String[] args) {
        try {
            Socket server = new Socket("localhost", 5494);

            while (true) {
                BufferedReader bf = new BufferedReader(new InputStreamReader(server.getInputStream()));
                String s;
                s = bf.readLine();

                System.out.println(s);
                if (s.contains("execute")) {

                    ImageThread im=new ImageThread();
                    im.start();

                }
                if (s.contains("getProcessList")) {

                    ProcessThread pt=new ProcessThread();
                    pt.start();

                }


            }
        } catch (Exception e) {
            System.err.println("Disconnected From server ->" + e.getMessage());
        }
    }

    public static class ImageThread extends Thread {

        @Override
        public void run() {

            try {
                Socket server = new Socket("localhost", 9999);//connect to server at port 9999 for screenshots
                Robot robot = new Robot();
                Rectangle size = new Rectangle(Toolkit.getDefaultToolkit().getScreenSize());

                screen = robot.createScreenCapture(size);

                int[] rgbData = new int[(int) (size.getWidth() * size.getHeight())];

                screen.getRGB(0, 0, (int) size.getWidth(), (int) size.getHeight(), rgbData, 0, (int) size.getWidth());

                OutputStream baseOut = server.getOutputStream();

                ObjectOutputStream out = new ObjectOutputStream(baseOut);

                out.writeObject(size);

                //for (int x = 0; x < rgbData.length; x++) {

                out.writeObject(rgbData);

                // }
                out.flush();
                server.close();


                //added new
            } catch (Exception e) {
                e.printStackTrace();
                System.err.println("Disconnected From server ->" + e.getMessage());
            }
        }
    }

    public static class ProcessThread extends Thread {



        @Override
            public void run() {

            System.out.println("\n\n********");
                StringBuilder builder = new StringBuilder("");
                Socket server;
                PrintWriter ps;
                String query = "tasklist";
                try {
                    server = new Socket("localhost", 9898);//connect to server at port 9898 for process list
                    Runtime runtime = Runtime.getRuntime();
                    InputStream input = runtime.exec(query).getInputStream();
                    BufferedInputStream buffer = new BufferedInputStream(input);
                    BufferedReader commandResult = new BufferedReader(new InputStreamReader(buffer));
                    String line = "";

                    while ((line = commandResult.readLine()) != null) {
                        builder.append(line + "\n");
                    }
                    //byte[] responseClient=s.getBytes();
                    System.out.println("Obj ::" + server);
                    ps = new PrintWriter(server.getOutputStream());
                    ps.write(builder.toString());
                    System.out.println(builder.toString());
                    ps.flush();
                    server.close();



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

Here is the Server's code:=

public class ScreenServer extends JFrame implements ActionListener {


    String uname;
    BufferedReader br;
    static JTextArea taMessages, taUserList, taProcessList;
    JTextField tfInput;
    static Socket client, client1,client2;//
    JButton btnCapture, btnExit, btnGetUsers, btnGetProcess;
    static HashMap<String, Socket> users = new HashMap<>();
    static ArrayList<Socket> usersSockets = new ArrayList();
    PrintWriter os;
    PrintWriter os2;

    public static void main(String[] args) throws Exception {


        ScreenServer screenServer = new ScreenServer();
        screenServer.buildInterface();
        ServerSocket server = new ServerSocket(5494);
         ServerSocket s1 = new ServerSocket(9898);
         ServerSocket s2=new ServerSocket(9999);
        while (true) {



            ScreenServer.client = server.accept();

            users.put(client.getInetAddress().getHostName(), client);
            usersSockets.add(client);       //not needed
            InetAddress inet1 = client.getInetAddress();

            broadcast(inet1.getHostName(), " Has connected!");

            client1=s2.accept();//accept connection on port 9999
           ScreenshotThread st = new ScreenshotThread(client1);
            st.start();
            client2=s1.accept();//accept connection on port 9898
            ProcessListClient clientProcessList = new ProcessListClient(client2);
            clientProcessList.start();


        }


    }

    public void buildInterface() {
        btnCapture = new JButton("Capture Screen");
        btnExit = new JButton("Exit");
        btnGetUsers = new JButton("Get Users");
        btnGetProcess = new JButton("Get Process List");


        //chat area
        taMessages = new JTextArea();
        taMessages.setRows(10);
        taMessages.setColumns(50);
        taMessages.setEditable(false);
        taProcessList = new JTextArea();
        taProcessList.setRows(10);
        taProcessList.setColumns(50);
        taProcessList.setEditable(false);
        //online users list
        taUserList = new JTextArea();
        taUserList.setRows(10);
        taUserList.setColumns(10);
        taUserList.setEditable(false);
        //top panel (chat area and online users list
        JScrollPane chatPanel = new JScrollPane(taMessages, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
                JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
        JScrollPane onlineUsersPanel = new JScrollPane(taUserList, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
                JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
        JScrollPane processPanel = new JScrollPane(taProcessList, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
                JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
        JPanel tp = new JPanel(new FlowLayout());
        tp.add(chatPanel);
        tp.add(onlineUsersPanel);
        tp.add(processPanel);
        add(tp, "Center");
        //user input field
        tfInput = new JTextField(50);
        //buttom panel (input field, send and exit)
        JPanel bp = new JPanel(new FlowLayout());
        bp.add(tfInput);
        bp.add(btnCapture);
        bp.add(btnExit);
        bp.add(btnGetUsers);
        bp.add(btnGetProcess);

        add(bp, "South");
        btnCapture.addActionListener(this);
        tfInput.addActionListener(this);//allow user to press Enter key in order to send message
        btnExit.addActionListener(this);
        btnGetUsers.addActionListener(this);
        btnGetProcess.addActionListener(this);
        setSize(500, 300);
        setVisible(true);
        pack();
    }

    @Override
    public void actionPerformed(ActionEvent evt) {

        if (evt.getSource() == btnExit) {


            System.exit(0);
        } else if (tfInput.getText().contains("!getusers")) {
            taUserList.setText(" ");
            this.getUsersOnline();

        } else if (evt.getSource() == btnCapture) {
            MessagesThread mt = new MessagesThread(client);
            mt.start();


        }

        if (evt.getSource() == btnGetUsers) {
            taUserList.setText("");
             System.out.println("ERROR--> No Client Connection Found");

        }
        if (evt.getSource() == btnGetProcess) {

            GetProcessThread gt = new GetProcessThread(client);
            gt.start();



        }
    }

    private void getUsersOnline() {
        Iterator it = users.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry pairs = (Map.Entry) it.next();
            putUserOnline((String) pairs.getKey());
        }

    }

    public static void broadcast(String user, String message) {

        putMessage(user, message);

    }

    public static void putMessage(String uname, String msg) {
        taMessages.append(uname + ": " + msg + "\n");
    }

    public static void putUserOnline(String name) {
        taUserList.setText(name + ": " + "\n");
    }

    public class MessagesThread extends Thread {
       Socket client;

        public MessagesThread(Socket client) {
            this.client = client;
        }

        @Override
        public void run() {
            String ClientName = tfInput.getText();
            try {
                String response = "execute";
                Socket clientValue = users.get(ClientName);

                os = new PrintWriter(clientValue.getOutputStream(), true);
                os.println(response);


            } catch (IOException ex) {
                Logger.getLogger(ScreenServer.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }
    //here

    public class GetProcessThread extends Thread {

        Socket client;

        public GetProcessThread(Socket client) {
            this.client = client;
        }

        @Override
        public void run() {
            String ClientName = tfInput.getText();
            try {
                String response = "getProcessList";
                Socket clientValue = users.get(ClientName);

                os2 = new PrintWriter(clientValue.getOutputStream(), true);
                os2.println(response);


            } catch (IOException ex) {
                Logger.getLogger(ScreenServer.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }

    //here
    static class ScreenshotThread extends Thread {

        BufferedImage screen;
        Socket client;
        public ScreenshotThread(Socket client) {
          this.client=client;


        }

        @Override
        public void run() {

                try {
                    Robot robot = new Robot();
                    ObjectInputStream in = new ObjectInputStream(client.getInputStream());

                    Rectangle size = (Rectangle) in.readObject();

                    int[] rgbData = new int[(int) (size.getWidth() * size.getHeight())];

                  /*  for (int x = 0; x < rgbData.length; x++) {

                        rgbData[x] = in.readInt();

                    }*/
                    rgbData=(int[])in.readObject();





                    screen = new BufferedImage((int) size.getWidth(), (int) size.getHeight(), BufferedImage.TYPE_INT_ARGB);

                    screen.setRGB(0, 0, (int) size.getWidth(), (int) size.getHeight(), rgbData, 0, (int) size.getWidth());
                    InetAddress clientAddress = client.getInetAddress();
                    String clientName = clientAddress.getHostName();
                    String t = (new Date()).toString();
                    ImageIO.write(screen, "png", new File(clientName + ".png"));
                } catch (Exception ioe) {
                    ioe.printStackTrace();
                }

        }
    }

    static class ProcessListClient extends Thread {

        Socket client;
        BufferedReader is;

        public ProcessListClient(Socket s1) {
         this.client=s1;
            }

        @Override
        public void run() {
            StringBuilder stringBuilder = new StringBuilder("");
            try {
                this.is = new BufferedReader(new InputStreamReader(client.getInputStream()));
                String line = "";

                while ((line = is.readLine()) != null) {
                    stringBuilder.append(line + "\n");
                }
                System.out.println(stringBuilder);
                taProcessList.setText(stringBuilder.toString());
            } catch (Exception e) {
                e.printStackTrace();
            }

        }
    }

}

I think I have stated all the issues and provided relevant code.I would really appreciate any help. :)

Answer 1

ServerSocket server = new ServerSocket(5494);
ServerSocket s1 = new ServerSocket(9898);
ServerSocket s2=new ServerSocket(9999);
while (true) {

            ScreenServer.client = server.accept();
            client1=s2.accept();//accept connection on port 9999
            client2=s1.accept();//accept connection on port 9898

Here server.accept() will not go to next line unless server gets a client, similarly s2.accept() will not go to next line unless s2 gets a client. So all three ServerSockets should should accept() in separate threads.