Help with a server program

Question

Hello,
I don't know much about threading, but I've got this server program (code follows). And where it does this... :
                    // Create a new thread for the connection
                    HandleAClient thread = new HandleAClient(connectToClient);
                    cn = clientNo;
                    // Start the new thread
                    thread.start();I need it to create another instance of the client program that accessing it with the same thread(I think, as i said I don't know much about threads). That way when a remote user accesses the client program, the server will automatically open another client program on the machine the server is running on. Then while their both using the same thread, they'll be able to speak back and forth without anyone else getting their text.
Does this make sense? Can anyone help?
Here is the server code, I don't have it perfected yet to send the text, but the clients will regester with the server.
// MultiThreadServer.java: The server can communicate with
// multiple clients concurrently using the multiple threads
import java.io.*;
import java.net.*;
import java.util.*;
// MultiThreadServer should be able to
//    handle text from multiple users at once
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MultiThreadServer extends JFrame {
     // Text area for displaying contents
     private JTextArea jta = new JTextArea();
     public static void main(String[] args) {
          new MultiThreadServer();
     public int cn = 0;
     public MultiThreadServer() {
          // Place text area on the frame
          getContentPane().setLayout(new BorderLayout());
          getContentPane().add(new JScrollPane(jta), BorderLayout.CENTER);
          setTitle("MultiThreadServer");
          setSize(500, 300);
          setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          setVisible(true); // It is necessary to show the frame here!
          try {
               // Create a server socket
               ServerSocket serverSocket = new ServerSocket(8000);
               jta.append("MultiThreadServer started at " + new Date() + '\n');
               // Number a client
               int clientNo = 1;
               while (true) {
                    // Listen for a new connection request
                    Socket connectToClient = serverSocket.accept();
                    // Display the client number
                    jta.append("Starting thread for client " + clientNo +
                         " at " + new Date() + '\n');
                    // Find the client's host name, and IP address
                    InetAddress clientInetAddress =
                         connectToClient.getInetAddress();
                    jta.append("Client " + clientNo + "'s host name is "
                         + clientInetAddress.getHostName() + "\n");
                    jta.append("Client " + clientNo + "'s IP Address is "
                         + clientInetAddress.getHostAddress() + "\n");
                    // Create a new thread for the connection
                    HandleAClient thread = new HandleAClient(connectToClient);
                    cn = clientNo;
                    // Start the new thread
                    thread.start();
                    // Increment clientNo
                    clientNo++;
          catch(IOException ex) {
               System.err.println(ex);
     // Inner class
     // Define the thread class for handling new connection
     class HandleAClient extends Thread {
          private Socket connectToClient; // A connected socket
          // Construct a thread
          public HandleAClient(Socket socket) {
               connectToClient = socket;
          // Run a thread
          public void run() {
               try {
                    // Create data input and output streams
                    DataInputStream isFromClient = new DataInputStream(
                         connectToClient.getInputStream());
                    DataOutputStream osToClient = new DataOutputStream(
                         connectToClient.getOutputStream());
                    osToClient.writeDouble(cn);
                    // Continuously serve the client
                    while (true) {
                         // Receive radius from the client
                         double radius = isFromClient.readDouble();
                         // Compute area
                         double area = radius*radius*Math.PI;
                         // Send area back to the client
                         osToClient.writeDouble(area);
                         jta.append("radius received from client: " +
                              radius + '\n');
                         jta.append("Area found: " + area + '\n');
               catch(IOException e) {
                    System.err.println(e);
}And here is the Client Program code, note that the sending of text does not yet work here either.
// Client.java: The client sends the input to the server and receives
//           result back from the server
import java.io.*;
import java.net.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.applet.*;
public class Client extends JFrame implements ActionListener {
     // Text field for receiving radius
     private JTextField jtf = new JTextField(40);
     // Text area to display contents
     private JTextArea jta = new JTextArea();
     // IO streams
     DataOutputStream osToServer;
     DataInputStream isFromServer;
     public static void main(String[] args) {
          new Client();
     public Client() {
          // Ask the user for a name
          String s = JOptionPane.showInputDialog
               (null, "Please Enter Your Name:", "ZedX Web Messenger", JOptionPane.QUESTION_MESSAGE);
          // Panel p to hold the label and text field
          JPanel p = new JPanel();
          p.setLayout(new BorderLayout());
          p.add(new JLabel("Enter Text"), BorderLayout.WEST);
          p.add(jtf, BorderLayout.CENTER);
          p.add(new JButton("Go"), BorderLayout.EAST);
          jtf.setHorizontalAlignment(JTextField.LEFT);
//          jta.editable(false);
          getContentPane().setLayout(new BorderLayout());
          getContentPane().add(p, BorderLayout.NORTH);
          getContentPane().add(new JScrollPane(jta), BorderLayout.CENTER);
          jtf.addActionListener(this); // Register listener
          String user = "Client";
          setTitle(user);
          setSize(500,500);
          setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          setVisible(true); // It is necessary to show the frame here!
          try {
               // Create a socket to connect to the server
               Socket connectToServer = new Socket("10.0.5.39", 8000);
               // Create an input stream to receive data from the server
               isFromServer = new DataInputStream(
                    connectToServer.getInputStream());
               // Create an output stream to send data to the server
               osToServer = new DataOutputStream(connectToServer.getOutputStream());
               // Send client Name to server
               // Get client number and name from server
               double cn = isFromServer.readDouble();
               user = user + " " + cn + ":  " + s;
               setTitle(user);
          catch (IOException ex) {
               jta.append(ex.toString() + '\n' + "Administrator must be offline, try again later.");
     public void actionPerformed(ActionEvent e) {
          String actionCommand = e.getActionCommand();
          if (e.getSource() instanceof JTextField) {
               try {
                    // Get the text from the text field
                    String radius = jtf.getText();
                    // Send the text to the server
                    osToServer.println(radius);
                    osToServer.flush();
                    // Get text from the server
                    double area = isFromServer.readDouble();
                    // Display to the text area
                    jta.append("You Sent: " + radius + "\n");
                    jta.append("Server" + area + '\n');
               catch (IOException ex) {
                    System.err.println(ex);
}

Answer 1

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