Client Freezes on socket() call

Question

Hi,
I'm trying to write a client that will connect to a server on a specified port and return the banner if there is any. I've tested the client with a local server and it seems to work fine, but when i attempt to connect to a host on the internet it freezes and a connections is never established (it seems to hang on the socket() call).
This is the client codd:
import java.net.*;
import java.io.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class bannerGrab extends JFrame implements ActionListener
      * GUI components
     private JButton connectButton, exitButton;
     private JLabel portLabel, ipLabel;
     private JTextField portField, ipField;
     private JTextArea outputArea;
     private JScrollPane scroller;
      * Network Components
     private Socket clientSocket;
      * Sets up the GUI and make ready for network connection
     public bannerGrab()
          super("Banner Grab v1.0 - kl365");
          Container c = getContentPane();
          c.setLayout(new FlowLayout());
           * Set u GUI components
          portLabel = new JLabel("Port Number:");
          ipLabel = new JLabel("IP Address: ");
          portField = new JTextField(5);
          ipField = new JTextField(10);
          outputArea = new JTextArea(15, 30);
          outputArea.setLineWrap(true);
          outputArea.setWrapStyleWord(true);
          scroller = new JScrollPane(outputArea);
          connectButton = new JButton("Connect");
          connectButton.addActionListener(this);
          exitButton = new JButton("Exit");
          exitButton.addActionListener(this);
          c.add(portLabel);
          c.add(portField);
          c.add(ipLabel);
          c.add(ipField);
          c.add(scroller);
          c.add(connectButton);
          c.add(exitButton);
          setSize(350, 400);
          show();
     public void actionPerformed(ActionEvent e)
          if(e.getSource() == exitButton)
            System.exit(0);
          if(e.getSource() == connectButton)
            setupConnection();
      * takes care of the socket initialization, connection and msg retrieval
     public void setupConnection()
          int portNumber = 0;
          String host;
         if(ipField.getText().equals(""))
              outputArea.append("Please input host address/name\n");
              return;
         if(!ipField.getText().equals("") && portField.getText().equals(""))
              portNumber = 21;
              host = ipField.getText();
         else
             try
                  portNumber = Integer.parseInt(portField.getText());                  
             catch(NumberFormatException nfe)
                  JOptionPane.showMessageDialog(this, "Port Number must be Integer value", "Number Format Exception",
                       JOptionPane.ERROR_MESSAGE);
                  portField.setText("");
                  return;
              host = ipField.getText();         
          * Attempt to connect to server
          try
               clientSocket = new Socket(host, portNumber);
          catch(UnknownHostException uhe)
               JOptionPane.showMessageDialog(this, "Invalid Host Name", "Unknown Host",
                    JOptionPane.ERROR_MESSAGE);     
               return;          
          catch(IOException e)
               JOptionPane.showMessageDialog(this, e.toString());
               return;
          outputArea.append("\n*****************************************************\n");              
         outputArea.append("Attempting Connection to " + host + " on port " + portNumber + "\n");
         BufferedReader inputStream;
          * retrieve msg from server if any is present
         try
              inputStream = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
              String inputString = "";
              outputArea.append("Receiving Message:\n\n");
              while((inputString = inputStream.readLine()) != null)
                   outputArea.append(inputString);
         catch(IOException e)
              JOptionPane.showMessageDialog(this, e.toString(),
                   "IOException", JOptionPane.ERROR_MESSAGE);                  
              return;         
     public static void main(String args[])
          bannerGrab app = new bannerGrab();
          app.addWindowListener(
               new WindowAdapter()
                    public void windowClosing(WindowEvent e)
                         System.exit(0);
}thanks for the help,
kl365

Answer 1

By "socket() call" you mean "new Socket(host, port)"?
Make sure it's there the program hangs: surround the call with debugging print()s; get a stack trace while it's hanging (Unix: control-backslash, Windows: control-break). Check the host name. Try with a numeric IP address. Try if "telnet host port" can open the connection. Is there a firewall that blocks access to the port? Does the hang time out after e.g. one minute?