Java Swing App hangs on socket loop

Question

H}ello everyone i've run into a bit of a snag with my application, its a simple chat bot right now but will evolve into a chat client soon. I can't do that however since my app hangs when i look through the readLine() function to receive data and i dont know how to fix this error. The code is below.
The doSocket() function is where the while loop is if anyone can help me with this i'd be very greatful.
* GuiFrame.java
* Created on August 13, 2008, 9:36 PM
import java.net.*;
import java.io.*;
import java.util.logging.Level;
import java.util.logging.Logger;
* @author  brian
public class GuiFrame extends javax.swing.JFrame {
    /** Creates new form GuiFrame */
    public GuiFrame() {
        initComponents();
    Socket client_sock = null;
    PrintWriter out = null;
    BufferedReader in = null;
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                         
    private void initComponents() {
        convertButton = new javax.swing.JButton();
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Test Bot");
        convertButton.setText("Connect");
        convertButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                convertButtonActionPerformed(evt);
        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(41, 41, 41)
                .addComponent(convertButton)
                .addContainerGap(42, Short.MAX_VALUE))
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(22, 22, 22)
                .addComponent(convertButton)
                .addContainerGap(26, Short.MAX_VALUE))
        pack();
    }// </editor-fold>                       
private void convertButtonActionPerformed(java.awt.event.ActionEvent evt) {                                             
    if (convertButton.getText()=="Connect") {
                String old;
                try {
                    client_sock = new Socket("www.spinchat.com", 3001);
                    out = new PrintWriter(client_sock.getOutputStream(), true);
                    in = new BufferedReader(new InputStreamReader(client_sock.getInputStream()));
                } catch (UnknownHostException e) {
                } catch (IOException e) {
            try {
                doSocket();
            } catch (IOException ex) {
                Logger.getLogger(GuiFrame.class.getName()).log(Level.SEVERE, null, ex);
    } else if (convertButton.getText()=="Disconnect") {
        out.println("e");
        out.close();
        try {
            client_sock.close();
            in.close();
        } catch (IOException ex) {
            Logger.getLogger(GuiFrame.class.getName()).log(Level.SEVERE, null, ex);
private void doSocket() throws IOException {
    BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
    String userInput;
    String old;
        while ((userInput = stdIn.readLine()) != null) {
            old = userInput;
            if (userInput != old) {
                String proto = userInput.substring(0, 0);
                if (proto == ":") {
                    out.println("{2");
                    out.println("BI'm a bot.");
                    out.println("aNICKHERE");
                    out.println("bPASSHERE");
                } else if (proto == "a") {
                    convertButton.setText("Disconnect");
                    out.println("JoinCHannel");
    * @param args the command line arguments
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new GuiFrame().setVisible(true);
    // Variables declaration - do not modify                    
    private javax.swing.JButton convertButton;
    // End of variables declaration                  
}Edited by: briansykes on Aug 13, 2008 9:55 PM
Edited by: briansykes on Aug 13, 2008 9:56 PM

Answer 1

>
..i've run into a bit of a snag with my application, its a simple chat bot right now but will evolve into a chat client soon. >Is this intended as a GUId app? If so, I would stick to using a GUI for input, rather than reading from the command line (which when I run it, is the DOS window that jumps up in the BG - quite counterintuitive). On the other hand, if it is intended as a non-GUId or headless app., it might be better to avoid any use of JComponents at all.
My edits stick to using a GUI.
Other notes:
- String comparison should be done as
s1.equals(s2)..rather than..
s1 == s2- Never [swallow exceptions|http://pscode.org/javafaq.html#stacktrace] in code that does not work.
- Some basic debugging skills are well called for here, to find where the program is getting stuck. When in doubt, print out!
- What made you think that
a) a test of equality on a member against which you had just set the value to the comparator, would logically lead to 'false'?
old = userInput;
if (userInput != old) ..b) A substring from indices '0 thru 0' would provide 1 character?
String proto = userInput.substring(0, 0);
if (proto == ":") ..
>
..if anyone can help me with this i'd be very greatful.>Gratitude is often best expressed through the offering of [Duke Stars|http://wikis.sun.com/display/SunForums/Duke+Stars+Program+Overview].
* GuiFrame.java
* Created on August 13, 2008, 9:36 PM
import java.net.*;
import java.io.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.*;
* @author  brian
public class GuiFrame extends JFrame {
    /** Creates new form GuiFrame */
    public GuiFrame() {
        initComponents();
    Socket client_sock = null;
    PrintWriter out = null;
    BufferedReader in = null;
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {
        convertButton = new JButton();
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setTitle("Test Bot");
        convertButton.setText("Connect");
        convertButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                convertButtonActionPerformed(evt);
        GroupLayout layout = new GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(41, 41, 41)
                .addComponent(convertButton)
                .addContainerGap(42, Short.MAX_VALUE))
        layout.setVerticalGroup(
            layout.createParallelGroup(GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(22, 22, 22)
                .addComponent(convertButton)
                .addContainerGap(26, Short.MAX_VALUE))
        pack();
        setLocationByPlatform(true);
    }// </editor-fold>
private void convertButtonActionPerformed(java.awt.event.ActionEvent evt) {
    if (convertButton.getText()=="Connect") {
                String old;
                try {
                    System.out.println( "Connect start.." );
                    client_sock = new Socket("www.spinchat.com", 3001);
                    out = new PrintWriter(client_sock.getOutputStream(), true);
                    in = new BufferedReader(new InputStreamReader(client_sock.getInputStream()));
                    System.out.println( "Connect end.." );
                } catch (UnknownHostException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
            try {
                doSocket();
            } catch (IOException ex) {
                Logger.getLogger(GuiFrame.class.getName()).log(Level.SEVERE, null, ex);
    } else if (convertButton.getText()=="Disconnect") {
        out.println("e");
        out.close();
        try {
            client_sock.close();
            in.close();
        } catch (IOException ex) {
            Logger.getLogger(GuiFrame.class.getName()).log(Level.SEVERE, null, ex);
    private void doSocket() throws IOException {
        System.out.println( "doSocket start.." );
        String userInput;
        String old;
        userInput = JOptionPane.showInputDialog(this, "Send..");
        while(userInput!=null && userInput.trim().length()>0) {
            System.out.println( "doSocket loop 1.." );
            String proto = userInput.substring(0, 1);
            System.out.println("proto: '" + proto + "'");
            if (proto.equals(":")) {
                System.out.println("Sending data..");
                out.println("{2");
                out.println("BI'm a bot.");
                out.println("aNICKHERE");
                out.println("bPASSHERE");
            } else if (proto.equals("a")) {
                convertButton.setText("Disconnect");
                out.println("JoinCHannel");
            userInput = JOptionPane.showInputDialog(this, "Send..");
        System.out.println( "doSocket end.." );
    * @param args the command line arguments
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new GuiFrame().setVisible(true);
    // Variables declaration - do not modify
    private JButton convertButton;
    // End of variables declaration
}