Applet Hangs when submitting data to servlet

Discussion in 'Java' started by ILPTAB, Aug 31, 2007.

  1. ILPTAB

    ILPTAB Guest

    I am currently supporting an interactive web site for a state agency.
    Recently we started getting reports from SOME of the users that the
    applet hangs when they attempt to submit data to the servlet running
    on our web server. We have not made any changes to the java code so
    the only thing I can figure is that it must be happening as a result
    of an update to the java JRE or Windows. Note that I said it's
    occurring with SOME of the users. Other people seem to be having no
    problem at all with it.

    To help illustrate the problem, I put together a small test server and
    applet that demonstrates the problem. I have included the source code
    for both parts below. On the applet side, it hangs when it comes to a
    line that attempts to instantiate the ObjectInputStream class and
    retrieve the input stream from the applet.

    ObjectInputStream inobj = new ObjectInputStream(s.getInputStream());

    Since the applet locks up, I am unable to give you any error messages
    in the java console. In fact the browser gets so locked up that it
    requires the user to close the session from the Windows task manager.

    On the Servlet side it hangs at the line that attempts to read the
    data stream from the socket connection.

    sSearchField_ = in.readLine();

    The error messages generated at the server are as follows:

    Java.lang.NullpointerException at ServerSide.testLookup(ServerSide.54)

    at ServerSide.run(ServerSide.java.98)

    at jave.lang.thread.run(Unkown Source)


    Any help in resolving this problem would be greatly appricated.

    Thank you.



    Here is the source code for both the Servlet and the applet.


    /* Class Name: AppletSide.java

    Copyright © 2007 Steve Rulison

    Version 1.0.0

    Purpose: This java applet will display relevent information
    pertaining to
    this examplet
    */

    import javax.swing.*;
    import javax.swing.event.*;
    import javax.swing.event.ListSelectionListener;
    import javax.swing.event.ListSelectionEvent;
    import javax.swing.table.*;
    import java.awt.*;
    import java.awt.event.*;
    import java.applet.*;

    import java.io.*;
    import java.util.*;
    import java.net.*;
    import java.lang.*;

    public class AppletSide extends JApplet
    implements ActionListener, KeyListener, MouseListener, Serializable
    {
    private static final long serialVersionUID = 1;

    private JButton theSubmitButton_, theClearButton_;
    private Socket s;
    private String host, ServerName_;
    private TestData td;
    private JPanel appletPanel, resultPanel, buttonPanel,
    socketPanel, headingPanel;
    private Font f1 = new Font("Sansserf", Font.BOLD, 28);

    private JLabel socketConnectionLabel = new JLabel("");
    private JTextField resultField1, resultField2, resultField3,
    resultField4, resultField5;

    private java.awt.List inquirylist;

    //Constructor
    public AppletSide()
    {
    headingPanel = new JPanel();
    headingPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

    //Initialize String variables for output.
    searchSetup();
    }//Constructor

    public void init()
    {
    // Note: The getCodeBase().getHost() methods must be invoked from
    the
    // init() method.
    ServerName_ = getCodeBase().getHost();
    System.out.println(ServerName_);

    System.out.println("Test Applet Version");
    }//End of init.

    //Establish a socket connection with the server.
    private boolean createSocket(String pServerName)
    {
    boolean SocketConnectSuccessful = false;
    try
    {
    int iPort = 554;
    s = new Socket(pServerName, iPort);
    SocketConnectSuccessful = true;
    socketConnectionLabel.setText("Socket connection successfully
    established with host " + pServerName + " on port " + iPort);
    socketPanel.validate();
    }
    catch(Exception e)
    {
    e.printStackTrace(System.err);
    System.out.println(e);
    SocketConnectSuccessful = false;
    socketConnectionRefused();
    }//End of catch block.
    return SocketConnectSuccessful;
    }//End of method createSocket.

    //This method is called when a socket connection could not be
    established.
    private void socketConnectionRefused()
    {
    socketConnectionLabel.setText("Unable to establish a connection with
    host. Please contact you network administrator.");
    socketPanel.validate();
    }//End of method socketConnectionRefused.

    //Setup search Inquiry labels.
    private void searchSetup()
    {
    setLayout(new BorderLayout());

    appletPanel = new JPanel();
    appletPanel.setLayout(new GridLayout(0,1));


    JLabel titleLabel = new JLabel("Test Page");
    titleLabel.setFont(f1);
    titleLabel.setForeground(Color.black);

    headingPanel.add(titleLabel);
    appletPanel.add(headingPanel);

    JPanel inquiryPanel = new JPanel();
    inquiryPanel.setLayout(new FlowLayout(FlowLayout.LEFT));

    JLabel inquiryLabel = new JLabel("Make Selection: ");
    inquiryPanel.add(inquiryLabel);

    inquirylist = new java.awt.List();
    inquirylist.add("Test 1");
    inquirylist.add("Test 2");
    inquirylist.add("Test 3");
    inquirylist.select(0);

    inquiryPanel.add(inquirylist);

    appletPanel.add(inquiryPanel);

    resultSetup();

    socketPanel = new JPanel();
    socketPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
    socketPanel.add(socketConnectionLabel);
    appletPanel.add(socketPanel);


    buttonPanel = new JPanel();
    buttonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

    theSubmitButton_ = new JButton("Submit");
    theSubmitButton_.addActionListener(this);
    theSubmitButton_.addKeyListener(this);

    buttonPanel.add(theSubmitButton_);
    theClearButton_ = new JButton("Clear");
    theClearButton_.addActionListener(this);
    theClearButton_.addKeyListener(this);
    buttonPanel.add(theClearButton_);
    appletPanel.add(buttonPanel);

    add(BorderLayout.CENTER, appletPanel);

    }//End of method searchLabelSetup.

    //Setup result labels.
    private void resultSetup()
    {
    resultPanel = new JPanel();
    resultPanel.setLayout(new GridLayout(5,2));

    JLabel resultLabel1 = new JLabel("Field 1: ", JLabel.RIGHT);
    JLabel resultLabel2 = new JLabel("Field 2: ", JLabel.RIGHT);
    JLabel resultLabel3 = new JLabel("Field 3: ", JLabel.RIGHT);
    JLabel resultLabel4 = new JLabel("Field 4: ", JLabel.RIGHT);
    JLabel resultLabel5 = new JLabel("Field 5: ", JLabel.RIGHT);

    resultField1 = new JTextField("Default value 1", 5);
    resultField1.setEditable(false);
    resultField2 = new JTextField("Default value 2 ",5);
    resultField2.setEditable(false);
    resultField3 = new JTextField("Default value 3",5);
    resultField3.setEditable(false);
    resultField4 = new JTextField("Default value 4",5);
    resultField4.setEditable(false);
    resultField5 = new JTextField("Default value 5",5);
    resultField5.setEditable(false);

    resultPanel.add(resultLabel1);
    resultPanel.add(resultField1);
    resultPanel.add(resultLabel2);
    resultPanel.add(resultField2);
    resultPanel.add(resultLabel3);
    resultPanel.add(resultField3);
    resultPanel.add(resultLabel4);
    resultPanel.add(resultField4);
    resultPanel.add(resultLabel5);
    resultPanel.add(resultField5);

    appletPanel.add(resultPanel);

    }//End of method resultLabelSetup.

    // Display the fields that have been populated with data received
    from the
    // server application.
    private void displayResults()
    {
    resultField1.setText(td.sField_1);
    resultField2.setText(td.sField_2);
    resultField3.setText(td.sField_3);
    resultField4.setText(td.sField_4);
    resultField5.setText(td.sField_5);
    resultPanel.validate();
    }//End of method displayResults.

    //Clears fields of data
    private void clearFields()
    {
    resultField1.setText("Default value 1");
    resultField2.setText("Default value 2");
    resultField3.setText("Default value 3");
    resultField4.setText("Default value 4");
    resultField5.setText("Default value 5");
    resultPanel.validate();
    inquirylist.select(0);
    }//End of method clearFields.

    //Reset the applet to allow the user to perform a new search.
    private void resetSearch()
    {
    this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
    clearFields();
    createSocket(ServerName_);
    this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
    }//End of method resetSearch.

    //Perform Input/Output operations with the server.
    private void serverIO()
    {
    this.setCursor(new Cursor(Cursor.WAIT_CURSOR));

    try
    {
    PrintWriter out =
    new PrintWriter(
    new BufferedWriter(
    new OutputStreamWriter(
    s.getOutputStream())),true);


    System.out.println("Check point 1 @ serverIO method.");
    out.println(inquirylist.getItem(inquirylist.getSelectedIndex()));
    // Thread.currentThread().sleep(5000);
    System.out.println("Check point 2 @ serverIO method.");
    //Read data back from server - Inputstream
    ObjectInputStream inObj = new
    ObjectInputStream(s.getInputStream());
    System.out.println("Check point 3 @ serverIO method.");
    out.flush();
    System.out.println("Check point 4 @ serverIO method.");

    td = (TestData) inObj.readObject();

    s.close();
    if(td.bRecFound)
    displayResults();
    else
    resetSearch();
    }
    catch(Exception e)
    {
    System.out.println("Check point 1 - Exception: " + e);

    }//End of try/catch block

    this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
    }//End of method ServerIO


    //Event handling method.
    public void actionPerformed(ActionEvent evt)
    {
    if(evt.getSource() == theClearButton_)
    {
    clearFields();
    repaint();
    }
    else if(evt.getSource() == theSubmitButton_)
    {
    if(createSocket(ServerName_))
    {
    System.getSecurityManager();

    // searchLabelSetup();
    validate();
    System.out.println(s.getInetAddress());
    serverIO();
    repaint();
    }
    else
    socketConnectionRefused();
    }
    }//End of method actionPerformed


    //Methodsfor handling for keyboard events
    public void keyPressed(KeyEvent evt){}
    public void keyReleased(KeyEvent evt){}
    public void keyTyped(KeyEvent evt)
    {
    // System.out.println(" " + (int)evt.getKeyChar() );

    if(evt.getSource() == theClearButton_)
    {
    clearFields();
    repaint();
    }
    else if(evt.getSource() == theSubmitButton_)
    {
    serverIO();
    repaint();
    }
    }//End of method keyTyped.

    public void mouseClicked(MouseEvent evt)
    {
    if(evt.getClickCount() == 2)
    {
    }
    }
    public void mouseExited(MouseEvent event){}
    public void mouseEntered(MouseEvent event){}
    public void mouseReleased(MouseEvent event){}
    public void mousePressed(MouseEvent event){}

    }//End of class ApplSide.

    class TestData implements Serializable
    {
    private static final long serialVersionUID = 1;

    /* Test Data */
    public String sField_1, sField_2, sField_3, sField_4, sField_5;
    public boolean bRecFound;

    //Constructor
    TestData()
    {}
    }//End of class ServerTestData.

    - - - - - - - - - - - - - - - - -
    - - - -

    /* Class name: ServerSide

    Author: Steven Rulison

    Purpose: Demonstrate the servlet side
    */

    import java.io.*;
    import java.util.*;
    import java.net.*;

    public class ServerSide extends Thread
    {
    private TestData td;
    private Socket s;
    private String sSearchField_;

    public static void main(String[] Args)
    {
    try
    {
    ServerSocket ss = new ServerSocket(554);

    int spawnCnt = 0;
    while(true)
    {
    Socket s = ss.accept();

    ++spawnCnt;
    System.out.println("Spawning " + spawnCnt);


    Thread servSide = new Thread(new ServerSide(s), "serverside");
    servSide.start();
    }
    }catch(IOException e)
    {
    e.printStackTrace(System.err);
    }
    }//End of main.


    //Constructor.
    public ServerSide(Socket s_)
    {
    s = s_;
    }//End of Constructor.


    private void testLookup(String sSearch)
    {
    td = new TestData();
    td.bRecFound = true;
    if(sSearch.trim().equals("Test 1"))
    {
    td.sField_1 = "Alpha";
    td.sField_2 = "Beta";
    td.sField_3 = "Gamma";
    td.sField_4 = "Delta";
    td.sField_5 = "Epsilon";
    }
    else if(sSearch.trim().equals("Test 2"))
    {
    td.sField_1 = "AAA";
    td.sField_2 = "BBB";
    td.sField_3 = "CCC";
    td.sField_4 = "DDDD";
    td.sField_5 = "EEEE";
    }
    else if(sSearch.trim().equals("Test 3"))
    {
    td.sField_1 = "111";
    td.sField_2 = "222";
    td.sField_3 = "333";
    td.sField_4 = "444";
    td.sField_5 = "555";
    }
    }// End of method testLookup.

    public void run()
    {
    try
    {
    //Setup Input Stream.
    BufferedReader in =
    new BufferedReader( new InputStreamReader(s.getInputStream()));

    // Setup output Stream.
    ObjectOutputStream ObjOut = new
    ObjectOutputStream(s.getOutputStream());

    //Perform intial read...
    sSearchField_ = in.readLine();

    Thread.currentThread().sleep(5000);

    System.out.println("The sSearchField_ variable = " + sSearchField_);

    testLookup(sSearchField_);

    ObjOut.writeObject(td);
    ObjOut.flush();
    ObjOut.close();

    s.close();
    }
    catch(Exception e)
    {
    e.printStackTrace(System.err);
    }
    }//End of run method
    }//End of ServerSide class...


    /*
    This is the class template that will be used to create the object
    that will
    be passed through to the ObjectInput/Output - stream to the lookup
    applet.
    */
    class TestData implements Serializable
    {
    private static final long serialVersionUID = 1;

    /* Test Data */
    public String sField_1, sField_2, sField_3, sField_4, sField_5;
    public boolean bRecFound;

    //Constructor
    TestData()
    {}

    }//End of class ServerTestData.
     
    ILPTAB, Aug 31, 2007
    #1
    1. Advertising

  2. ILPTAB wrote:
    > I am currently supporting an interactive web site for a state agency.
    > Recently we started getting reports from SOME of the users that the
    > applet hangs when they attempt to submit data to the servlet running
    > on our web server. We have not made any changes to the java code so
    > the only thing I can figure is that it must be happening as a result
    > of an update to the java JRE or Windows. Note that I said it's
    > occurring with SOME of the users. Other people seem to be having no
    > problem at all with it.
    >
    > To help illustrate the problem, I put together a small test server and
    > applet that demonstrates the problem. I have included the source code
    > for both parts below. On the applet side, it hangs when it comes to a
    > line that attempts to instantiate the ObjectInputStream class and
    > retrieve the input stream from the applet.
    >
    > ObjectInputStream inobj = new ObjectInputStream(s.getInputStream());
    >
    > Since the applet locks up, I am unable to give you any error messages
    > in the java console. In fact the browser gets so locked up that it
    > requires the user to close the session from the Windows task manager.
    >
    > On the Servlet side it hangs at the line that attempts to read the
    > data stream from the socket connection.
    >
    > sSearchField_ = in.readLine();
    >
    > The error messages generated at the server are as follows:
    >
    > Java.lang.NullpointerException at ServerSide.testLookup(ServerSide.54)
    >
    > at ServerSide.run(ServerSide.java.98)
    >
    > at jave.lang.thread.run(Unkown Source)
    >
    >
    > Any help in resolving this problem would be greatly appricated.
    >
    > Thank you.
    >
    >
    >
    > Here is the source code for both the Servlet and the applet.
    >
    >
    > /* Class Name: AppletSide.java
    >
    > Copyright © 2007 Steve Rulison
    >
    > Version 1.0.0
    >
    > Purpose: This java applet will display relevent information
    > pertaining to
    > this examplet
    > */
    >
    > import javax.swing.*;
    > import javax.swing.event.*;
    > import javax.swing.event.ListSelectionListener;
    > import javax.swing.event.ListSelectionEvent;
    > import javax.swing.table.*;
    > import java.awt.*;
    > import java.awt.event.*;
    > import java.applet.*;
    >
    > import java.io.*;
    > import java.util.*;
    > import java.net.*;
    > import java.lang.*;
    >
    > public class AppletSide extends JApplet
    > implements ActionListener, KeyListener, MouseListener, Serializable
    > {
    > private static final long serialVersionUID = 1;
    >
    > private JButton theSubmitButton_, theClearButton_;
    > private Socket s;
    > private String host, ServerName_;
    > private TestData td;
    > private JPanel appletPanel, resultPanel, buttonPanel,
    > socketPanel, headingPanel;
    > private Font f1 = new Font("Sansserf", Font.BOLD, 28);
    >
    > private JLabel socketConnectionLabel = new JLabel("");
    > private JTextField resultField1, resultField2, resultField3,
    > resultField4, resultField5;
    >
    > private java.awt.List inquirylist;
    >
    > //Constructor
    > public AppletSide()
    > {
    > headingPanel = new JPanel();
    > headingPanel.setLayout(new FlowLayout(FlowLayout.CENTER));
    >
    > //Initialize String variables for output.
    > searchSetup();
    > }//Constructor
    >
    > public void init()
    > {
    > // Note: The getCodeBase().getHost() methods must be invoked from
    > the
    > // init() method.
    > ServerName_ = getCodeBase().getHost();
    > System.out.println(ServerName_);
    >
    > System.out.println("Test Applet Version");
    > }//End of init.
    >
    > //Establish a socket connection with the server.
    > private boolean createSocket(String pServerName)
    > {
    > boolean SocketConnectSuccessful = false;
    > try
    > {
    > int iPort = 554;
    > s = new Socket(pServerName, iPort);
    > SocketConnectSuccessful = true;
    > socketConnectionLabel.setText("Socket connection successfully
    > established with host " + pServerName + " on port " + iPort);
    > socketPanel.validate();
    > }
    > catch(Exception e)
    > {
    > e.printStackTrace(System.err);
    > System.out.println(e);
    > SocketConnectSuccessful = false;
    > socketConnectionRefused();
    > }//End of catch block.
    > return SocketConnectSuccessful;
    > }//End of method createSocket.
    >
    > //This method is called when a socket connection could not be
    > established.
    > private void socketConnectionRefused()
    > {
    > socketConnectionLabel.setText("Unable to establish a connection with
    > host. Please contact you network administrator.");
    > socketPanel.validate();
    > }//End of method socketConnectionRefused.
    >
    > //Setup search Inquiry labels.
    > private void searchSetup()
    > {
    > setLayout(new BorderLayout());
    >
    > appletPanel = new JPanel();
    > appletPanel.setLayout(new GridLayout(0,1));
    >
    >
    > JLabel titleLabel = new JLabel("Test Page");
    > titleLabel.setFont(f1);
    > titleLabel.setForeground(Color.black);
    >
    > headingPanel.add(titleLabel);
    > appletPanel.add(headingPanel);
    >
    > JPanel inquiryPanel = new JPanel();
    > inquiryPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
    >
    > JLabel inquiryLabel = new JLabel("Make Selection: ");
    > inquiryPanel.add(inquiryLabel);
    >
    > inquirylist = new java.awt.List();
    > inquirylist.add("Test 1");
    > inquirylist.add("Test 2");
    > inquirylist.add("Test 3");
    > inquirylist.select(0);
    >
    > inquiryPanel.add(inquirylist);
    >
    > appletPanel.add(inquiryPanel);
    >
    > resultSetup();
    >
    > socketPanel = new JPanel();
    > socketPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
    > socketPanel.add(socketConnectionLabel);
    > appletPanel.add(socketPanel);
    >
    >
    > buttonPanel = new JPanel();
    > buttonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));
    >
    > theSubmitButton_ = new JButton("Submit");
    > theSubmitButton_.addActionListener(this);
    > theSubmitButton_.addKeyListener(this);
    >
    > buttonPanel.add(theSubmitButton_);
    > theClearButton_ = new JButton("Clear");
    > theClearButton_.addActionListener(this);
    > theClearButton_.addKeyListener(this);
    > buttonPanel.add(theClearButton_);
    > appletPanel.add(buttonPanel);
    >
    > add(BorderLayout.CENTER, appletPanel);
    >
    > }//End of method searchLabelSetup.
    >
    > //Setup result labels.
    > private void resultSetup()
    > {
    > resultPanel = new JPanel();
    > resultPanel.setLayout(new GridLayout(5,2));
    >
    > JLabel resultLabel1 = new JLabel("Field 1: ", JLabel.RIGHT);
    > JLabel resultLabel2 = new JLabel("Field 2: ", JLabel.RIGHT);
    > JLabel resultLabel3 = new JLabel("Field 3: ", JLabel.RIGHT);
    > JLabel resultLabel4 = new JLabel("Field 4: ", JLabel.RIGHT);
    > JLabel resultLabel5 = new JLabel("Field 5: ", JLabel.RIGHT);
    >
    > resultField1 = new JTextField("Default value 1", 5);
    > resultField1.setEditable(false);
    > resultField2 = new JTextField("Default value 2 ",5);
    > resultField2.setEditable(false);
    > resultField3 = new JTextField("Default value 3",5);
    > resultField3.setEditable(false);
    > resultField4 = new JTextField("Default value 4",5);
    > resultField4.setEditable(false);
    > resultField5 = new JTextField("Default value 5",5);
    > resultField5.setEditable(false);
    >
    > resultPanel.add(resultLabel1);
    > resultPanel.add(resultField1);
    > resultPanel.add(resultLabel2);
    > resultPanel.add(resultField2);
    > resultPanel.add(resultLabel3);
    > resultPanel.add(resultField3);
    > resultPanel.add(resultLabel4);
    > resultPanel.add(resultField4);
    > resultPanel.add(resultLabel5);
    > resultPanel.add(resultField5);
    >
    > appletPanel.add(resultPanel);
    >
    > }//End of method resultLabelSetup.
    >
    > // Display the fields that have been populated with data received
    > from the
    > // server application.
    > private void displayResults()
    > {
    > resultField1.setText(td.sField_1);
    > resultField2.setText(td.sField_2);
    > resultField3.setText(td.sField_3);
    > resultField4.setText(td.sField_4);
    > resultField5.setText(td.sField_5);
    > resultPanel.validate();
    > }//End of method displayResults.
    >
    > //Clears fields of data
    > private void clearFields()
    > {
    > resultField1.setText("Default value 1");
    > resultField2.setText("Default value 2");
    > resultField3.setText("Default value 3");
    > resultField4.setText("Default value 4");
    > resultField5.setText("Default value 5");
    > resultPanel.validate();
    > inquirylist.select(0);
    > }//End of method clearFields.
    >
    > //Reset the applet to allow the user to perform a new search.
    > private void resetSearch()
    > {
    > this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
    > clearFields();
    > createSocket(ServerName_);
    > this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
    > }//End of method resetSearch.
    >
    > //Perform Input/Output operations with the server.
    > private void serverIO()
    > {
    > this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
    >
    > try
    > {
    > PrintWriter out =
    > new PrintWriter(
    > new BufferedWriter(
    > new OutputStreamWriter(
    > s.getOutputStream())),true);
    >
    >
    > System.out.println("Check point 1 @ serverIO method.");
    > out.println(inquirylist.getItem(inquirylist.getSelectedIndex()));
    > // Thread.currentThread().sleep(5000);
    > System.out.println("Check point 2 @ serverIO method.");
    > //Read data back from server - Inputstream
    > ObjectInputStream inObj = new
    > ObjectInputStream(s.getInputStream());
    > System.out.println("Check point 3 @ serverIO method.");
    > out.flush();
    > System.out.println("Check point 4 @ serverIO method.");
    >
    > td = (TestData) inObj.readObject();
    >
    > s.close();
    > if(td.bRecFound)
    > displayResults();
    > else
    > resetSearch();
    > }
    > catch(Exception e)
    > {
    > System.out.println("Check point 1 - Exception: " + e);
    >
    > }//End of try/catch block
    >
    > this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
    > }//End of method ServerIO
    >
    >
    > //Event handling method.
    > public void actionPerformed(ActionEvent evt)
    > {
    > if(evt.getSource() == theClearButton_)
    > {
    > clearFields();
    > repaint();
    > }
    > else if(evt.getSource() == theSubmitButton_)
    > {
    > if(createSocket(ServerName_))
    > {
    > System.getSecurityManager();
    >
    > // searchLabelSetup();
    > validate();
    > System.out.println(s.getInetAddress());
    > serverIO();
    > repaint();
    > }
    > else
    > socketConnectionRefused();
    > }
    > }//End of method actionPerformed
    >
    >
    > //Methodsfor handling for keyboard events
    > public void keyPressed(KeyEvent evt){}
    > public void keyReleased(KeyEvent evt){}
    > public void keyTyped(KeyEvent evt)
    > {
    > // System.out.println(" " + (int)evt.getKeyChar() );
    >
    > if(evt.getSource() == theClearButton_)
    > {
    > clearFields();
    > repaint();
    > }
    > else if(evt.getSource() == theSubmitButton_)
    > {
    > serverIO();
    > repaint();
    > }
    > }//End of method keyTyped.
    >
    > public void mouseClicked(MouseEvent evt)
    > {
    > if(evt.getClickCount() == 2)
    > {
    > }
    > }
    > public void mouseExited(MouseEvent event){}
    > public void mouseEntered(MouseEvent event){}
    > public void mouseReleased(MouseEvent event){}
    > public void mousePressed(MouseEvent event){}
    >
    > }//End of class ApplSide.
    >
    > class TestData implements Serializable
    > {
    > private static final long serialVersionUID = 1;
    >
    > /* Test Data */
    > public String sField_1, sField_2, sField_3, sField_4, sField_5;
    > public boolean bRecFound;
    >
    > //Constructor
    > TestData()
    > {}
    > }//End of class ServerTestData.
    >
    > - - - - - - - - - - - - - - - - -
    > - - - -
    >
    > /* Class name: ServerSide
    >
    > Author: Steven Rulison
    >
    > Purpose: Demonstrate the servlet side
    > */
    >
    > import java.io.*;
    > import java.util.*;
    > import java.net.*;
    >
    > public class ServerSide extends Thread
    > {
    > private TestData td;
    > private Socket s;
    > private String sSearchField_;
    >
    > public static void main(String[] Args)
    > {
    > try
    > {
    > ServerSocket ss = new ServerSocket(554);
    >
    > int spawnCnt = 0;
    > while(true)
    > {
    > Socket s = ss.accept();
    >
    > ++spawnCnt;
    > System.out.println("Spawning " + spawnCnt);
    >
    >
    > Thread servSide = new Thread(new ServerSide(s), "serverside");
    > servSide.start();
    > }
    > }catch(IOException e)
    > {
    > e.printStackTrace(System.err);
    > }
    > }//End of main.
    >
    >
    > //Constructor.
    > public ServerSide(Socket s_)
    > {
    > s = s_;
    > }//End of Constructor.
    >
    >
    > private void testLookup(String sSearch)
    > {
    > td = new TestData();
    > td.bRecFound = true;
    > if(sSearch.trim().equals("Test 1"))
    > {
    > td.sField_1 = "Alpha";
    > td.sField_2 = "Beta";
    > td.sField_3 = "Gamma";
    > td.sField_4 = "Delta";
    > td.sField_5 = "Epsilon";
    > }
    > else if(sSearch.trim().equals("Test 2"))
    > {
    > td.sField_1 = "AAA";
    > td.sField_2 = "BBB";
    > td.sField_3 = "CCC";
    > td.sField_4 = "DDDD";
    > td.sField_5 = "EEEE";
    > }
    > else if(sSearch.trim().equals("Test 3"))
    > {
    > td.sField_1 = "111";
    > td.sField_2 = "222";
    > td.sField_3 = "333";
    > td.sField_4 = "444";
    > td.sField_5 = "555";
    > }
    > }// End of method testLookup.
    >
    > public void run()
    > {
    > try
    > {
    > //Setup Input Stream.
    > BufferedReader in =
    > new BufferedReader( new InputStreamReader(s.getInputStream()));
    >
    > // Setup output Stream.
    > ObjectOutputStream ObjOut = new
    > ObjectOutputStream(s.getOutputStream());
    >
    > //Perform intial read...
    > sSearchField_ = in.readLine();
    >
    > Thread.currentThread().sleep(5000);
    >
    > System.out.println("The sSearchField_ variable = " + sSearchField_);
    >
    > testLookup(sSearchField_);
    >
    > ObjOut.writeObject(td);
    > ObjOut.flush();
    > ObjOut.close();
    >
    > s.close();
    > }
    > catch(Exception e)
    > {
    > e.printStackTrace(System.err);
    > }
    > }//End of run method
    > }//End of ServerSide class...
    >
    >
    > /*
    > This is the class template that will be used to create the object
    > that will
    > be passed through to the ObjectInput/Output - stream to the lookup
    > applet.
    > */
    > class TestData implements Serializable
    > {
    > private static final long serialVersionUID = 1;
    >
    > /* Test Data */
    > public String sField_1, sField_2, sField_3, sField_4, sField_5;
    > public boolean bRecFound;
    >
    > //Constructor
    > TestData()
    > {}
    >
    > }//End of class ServerTestData.
    >


    I have seen similar problems with applications. I cannot duplicate the
    problem and it only happens once in a while. I'm getting socket I/O
    hangs not just with ObjectOutputStream/InputStreams but with binary I/O
    too. It started for me in May or June on an application that had been
    running for over a year with no problems. It lasted several weeks and I
    hadn't seen it again until about a week ago. That could be just
    coincidence though. The computers I'm using are not being updated so I
    don't think that is the problem.

    The socket did not time out and I created another timer that closed the
    socket if it was still open and that didn't work. I'm at a loss as to
    what is happening and don't really know where to look. My client is not
    very happy with me at the moment.

    --

    Knute Johnson
    email s/nospam/knute/
     
    Knute Johnson, Aug 31, 2007
    #2
    1. Advertising

  3. Hi,

    I don't know what is causing the hang but FWIW I use the following Timeouts
    to put a time limit on my socket connections and socket reads. At least then
    you be able to identify which read isn't being satisfied and track down what
    happened to the writer.

    t3Sock.connect(new InetSocketAddress(host,port), CONTIMOUT);

    : : :

    public void setTimeout(int msecs) throws UnknownHostException, IOException
    {
    t3Sock.setSoTimeout(msecs);
    }

    Cheers Richard Maher

    "ILPTAB" <> wrote in message
    news:...
    I am currently supporting an interactive web site for a state agency.
    Recently we started getting reports from SOME of the users that the
    applet hangs when they attempt to submit data to the servlet running
    on our web server. We have not made any changes to the java code so
    the only thing I can figure is that it must be happening as a result
    of an update to the java JRE or Windows. Note that I said it's
    occurring with SOME of the users. Other people seem to be having no
    problem at all with it.

    To help illustrate the problem, I put together a small test server and
    applet that demonstrates the problem. I have included the source code
    for both parts below. On the applet side, it hangs when it comes to a
    line that attempts to instantiate the ObjectInputStream class and
    retrieve the input stream from the applet.

    ObjectInputStream inobj = new ObjectInputStream(s.getInputStream());

    Since the applet locks up, I am unable to give you any error messages
    in the java console. In fact the browser gets so locked up that it
    requires the user to close the session from the Windows task manager.

    On the Servlet side it hangs at the line that attempts to read the
    data stream from the socket connection.

    sSearchField_ = in.readLine();

    The error messages generated at the server are as follows:

    Java.lang.NullpointerException at ServerSide.testLookup(ServerSide.54)

    at ServerSide.run(ServerSide.java.98)

    at jave.lang.thread.run(Unkown Source)


    Any help in resolving this problem would be greatly appricated.

    Thank you.



    Here is the source code for both the Servlet and the applet.


    /* Class Name: AppletSide.java

    Copyright © 2007 Steve Rulison

    Version 1.0.0

    Purpose: This java applet will display relevent information
    pertaining to
    this examplet
    */

    import javax.swing.*;
    import javax.swing.event.*;
    import javax.swing.event.ListSelectionListener;
    import javax.swing.event.ListSelectionEvent;
    import javax.swing.table.*;
    import java.awt.*;
    import java.awt.event.*;
    import java.applet.*;

    import java.io.*;
    import java.util.*;
    import java.net.*;
    import java.lang.*;

    public class AppletSide extends JApplet
    implements ActionListener, KeyListener, MouseListener, Serializable
    {
    private static final long serialVersionUID = 1;

    private JButton theSubmitButton_, theClearButton_;
    private Socket s;
    private String host, ServerName_;
    private TestData td;
    private JPanel appletPanel, resultPanel, buttonPanel,
    socketPanel, headingPanel;
    private Font f1 = new Font("Sansserf", Font.BOLD, 28);

    private JLabel socketConnectionLabel = new JLabel("");
    private JTextField resultField1, resultField2, resultField3,
    resultField4, resultField5;

    private java.awt.List inquirylist;

    //Constructor
    public AppletSide()
    {
    headingPanel = new JPanel();
    headingPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

    //Initialize String variables for output.
    searchSetup();
    }//Constructor

    public void init()
    {
    // Note: The getCodeBase().getHost() methods must be invoked from
    the
    // init() method.
    ServerName_ = getCodeBase().getHost();
    System.out.println(ServerName_);

    System.out.println("Test Applet Version");
    }//End of init.

    //Establish a socket connection with the server.
    private boolean createSocket(String pServerName)
    {
    boolean SocketConnectSuccessful = false;
    try
    {
    int iPort = 554;
    s = new Socket(pServerName, iPort);
    SocketConnectSuccessful = true;
    socketConnectionLabel.setText("Socket connection successfully
    established with host " + pServerName + " on port " + iPort);
    socketPanel.validate();
    }
    catch(Exception e)
    {
    e.printStackTrace(System.err);
    System.out.println(e);
    SocketConnectSuccessful = false;
    socketConnectionRefused();
    }//End of catch block.
    return SocketConnectSuccessful;
    }//End of method createSocket.

    //This method is called when a socket connection could not be
    established.
    private void socketConnectionRefused()
    {
    socketConnectionLabel.setText("Unable to establish a connection with
    host. Please contact you network administrator.");
    socketPanel.validate();
    }//End of method socketConnectionRefused.

    //Setup search Inquiry labels.
    private void searchSetup()
    {
    setLayout(new BorderLayout());

    appletPanel = new JPanel();
    appletPanel.setLayout(new GridLayout(0,1));


    JLabel titleLabel = new JLabel("Test Page");
    titleLabel.setFont(f1);
    titleLabel.setForeground(Color.black);

    headingPanel.add(titleLabel);
    appletPanel.add(headingPanel);

    JPanel inquiryPanel = new JPanel();
    inquiryPanel.setLayout(new FlowLayout(FlowLayout.LEFT));

    JLabel inquiryLabel = new JLabel("Make Selection: ");
    inquiryPanel.add(inquiryLabel);

    inquirylist = new java.awt.List();
    inquirylist.add("Test 1");
    inquirylist.add("Test 2");
    inquirylist.add("Test 3");
    inquirylist.select(0);

    inquiryPanel.add(inquirylist);

    appletPanel.add(inquiryPanel);

    resultSetup();

    socketPanel = new JPanel();
    socketPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
    socketPanel.add(socketConnectionLabel);
    appletPanel.add(socketPanel);


    buttonPanel = new JPanel();
    buttonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

    theSubmitButton_ = new JButton("Submit");
    theSubmitButton_.addActionListener(this);
    theSubmitButton_.addKeyListener(this);

    buttonPanel.add(theSubmitButton_);
    theClearButton_ = new JButton("Clear");
    theClearButton_.addActionListener(this);
    theClearButton_.addKeyListener(this);
    buttonPanel.add(theClearButton_);
    appletPanel.add(buttonPanel);

    add(BorderLayout.CENTER, appletPanel);

    }//End of method searchLabelSetup.

    //Setup result labels.
    private void resultSetup()
    {
    resultPanel = new JPanel();
    resultPanel.setLayout(new GridLayout(5,2));

    JLabel resultLabel1 = new JLabel("Field 1: ", JLabel.RIGHT);
    JLabel resultLabel2 = new JLabel("Field 2: ", JLabel.RIGHT);
    JLabel resultLabel3 = new JLabel("Field 3: ", JLabel.RIGHT);
    JLabel resultLabel4 = new JLabel("Field 4: ", JLabel.RIGHT);
    JLabel resultLabel5 = new JLabel("Field 5: ", JLabel.RIGHT);

    resultField1 = new JTextField("Default value 1", 5);
    resultField1.setEditable(false);
    resultField2 = new JTextField("Default value 2 ",5);
    resultField2.setEditable(false);
    resultField3 = new JTextField("Default value 3",5);
    resultField3.setEditable(false);
    resultField4 = new JTextField("Default value 4",5);
    resultField4.setEditable(false);
    resultField5 = new JTextField("Default value 5",5);
    resultField5.setEditable(false);

    resultPanel.add(resultLabel1);
    resultPanel.add(resultField1);
    resultPanel.add(resultLabel2);
    resultPanel.add(resultField2);
    resultPanel.add(resultLabel3);
    resultPanel.add(resultField3);
    resultPanel.add(resultLabel4);
    resultPanel.add(resultField4);
    resultPanel.add(resultLabel5);
    resultPanel.add(resultField5);

    appletPanel.add(resultPanel);

    }//End of method resultLabelSetup.

    // Display the fields that have been populated with data received
    from the
    // server application.
    private void displayResults()
    {
    resultField1.setText(td.sField_1);
    resultField2.setText(td.sField_2);
    resultField3.setText(td.sField_3);
    resultField4.setText(td.sField_4);
    resultField5.setText(td.sField_5);
    resultPanel.validate();
    }//End of method displayResults.

    //Clears fields of data
    private void clearFields()
    {
    resultField1.setText("Default value 1");
    resultField2.setText("Default value 2");
    resultField3.setText("Default value 3");
    resultField4.setText("Default value 4");
    resultField5.setText("Default value 5");
    resultPanel.validate();
    inquirylist.select(0);
    }//End of method clearFields.

    //Reset the applet to allow the user to perform a new search.
    private void resetSearch()
    {
    this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
    clearFields();
    createSocket(ServerName_);
    this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
    }//End of method resetSearch.

    //Perform Input/Output operations with the server.
    private void serverIO()
    {
    this.setCursor(new Cursor(Cursor.WAIT_CURSOR));

    try
    {
    PrintWriter out =
    new PrintWriter(
    new BufferedWriter(
    new OutputStreamWriter(
    s.getOutputStream())),true);


    System.out.println("Check point 1 @ serverIO method.");
    out.println(inquirylist.getItem(inquirylist.getSelectedIndex()));
    // Thread.currentThread().sleep(5000);
    System.out.println("Check point 2 @ serverIO method.");
    //Read data back from server - Inputstream
    ObjectInputStream inObj = new
    ObjectInputStream(s.getInputStream());
    System.out.println("Check point 3 @ serverIO method.");
    out.flush();
    System.out.println("Check point 4 @ serverIO method.");

    td = (TestData) inObj.readObject();

    s.close();
    if(td.bRecFound)
    displayResults();
    else
    resetSearch();
    }
    catch(Exception e)
    {
    System.out.println("Check point 1 - Exception: " + e);

    }//End of try/catch block

    this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
    }//End of method ServerIO


    //Event handling method.
    public void actionPerformed(ActionEvent evt)
    {
    if(evt.getSource() == theClearButton_)
    {
    clearFields();
    repaint();
    }
    else if(evt.getSource() == theSubmitButton_)
    {
    if(createSocket(ServerName_))
    {
    System.getSecurityManager();

    // searchLabelSetup();
    validate();
    System.out.println(s.getInetAddress());
    serverIO();
    repaint();
    }
    else
    socketConnectionRefused();
    }
    }//End of method actionPerformed


    //Methodsfor handling for keyboard events
    public void keyPressed(KeyEvent evt){}
    public void keyReleased(KeyEvent evt){}
    public void keyTyped(KeyEvent evt)
    {
    // System.out.println(" " + (int)evt.getKeyChar() );

    if(evt.getSource() == theClearButton_)
    {
    clearFields();
    repaint();
    }
    else if(evt.getSource() == theSubmitButton_)
    {
    serverIO();
    repaint();
    }
    }//End of method keyTyped.

    public void mouseClicked(MouseEvent evt)
    {
    if(evt.getClickCount() == 2)
    {
    }
    }
    public void mouseExited(MouseEvent event){}
    public void mouseEntered(MouseEvent event){}
    public void mouseReleased(MouseEvent event){}
    public void mousePressed(MouseEvent event){}

    }//End of class ApplSide.

    class TestData implements Serializable
    {
    private static final long serialVersionUID = 1;

    /* Test Data */
    public String sField_1, sField_2, sField_3, sField_4, sField_5;
    public boolean bRecFound;

    //Constructor
    TestData()
    {}
    }//End of class ServerTestData.

    - - - - - - - - - - - - - - - - -
    - - - -

    /* Class name: ServerSide

    Author: Steven Rulison

    Purpose: Demonstrate the servlet side
    */

    import java.io.*;
    import java.util.*;
    import java.net.*;

    public class ServerSide extends Thread
    {
    private TestData td;
    private Socket s;
    private String sSearchField_;

    public static void main(String[] Args)
    {
    try
    {
    ServerSocket ss = new ServerSocket(554);

    int spawnCnt = 0;
    while(true)
    {
    Socket s = ss.accept();

    ++spawnCnt;
    System.out.println("Spawning " + spawnCnt);


    Thread servSide = new Thread(new ServerSide(s), "serverside");
    servSide.start();
    }
    }catch(IOException e)
    {
    e.printStackTrace(System.err);
    }
    }//End of main.


    //Constructor.
    public ServerSide(Socket s_)
    {
    s = s_;
    }//End of Constructor.


    private void testLookup(String sSearch)
    {
    td = new TestData();
    td.bRecFound = true;
    if(sSearch.trim().equals("Test 1"))
    {
    td.sField_1 = "Alpha";
    td.sField_2 = "Beta";
    td.sField_3 = "Gamma";
    td.sField_4 = "Delta";
    td.sField_5 = "Epsilon";
    }
    else if(sSearch.trim().equals("Test 2"))
    {
    td.sField_1 = "AAA";
    td.sField_2 = "BBB";
    td.sField_3 = "CCC";
    td.sField_4 = "DDDD";
    td.sField_5 = "EEEE";
    }
    else if(sSearch.trim().equals("Test 3"))
    {
    td.sField_1 = "111";
    td.sField_2 = "222";
    td.sField_3 = "333";
    td.sField_4 = "444";
    td.sField_5 = "555";
    }
    }// End of method testLookup.

    public void run()
    {
    try
    {
    //Setup Input Stream.
    BufferedReader in =
    new BufferedReader( new InputStreamReader(s.getInputStream()));

    // Setup output Stream.
    ObjectOutputStream ObjOut = new
    ObjectOutputStream(s.getOutputStream());

    //Perform intial read...
    sSearchField_ = in.readLine();

    Thread.currentThread().sleep(5000);

    System.out.println("The sSearchField_ variable = " + sSearchField_);

    testLookup(sSearchField_);

    ObjOut.writeObject(td);
    ObjOut.flush();
    ObjOut.close();

    s.close();
    }
    catch(Exception e)
    {
    e.printStackTrace(System.err);
    }
    }//End of run method
    }//End of ServerSide class...


    /*
    This is the class template that will be used to create the object
    that will
    be passed through to the ObjectInput/Output - stream to the lookup
    applet.
    */
    class TestData implements Serializable
    {
    private static final long serialVersionUID = 1;

    /* Test Data */
    public String sField_1, sField_2, sField_3, sField_4, sField_5;
    public boolean bRecFound;

    //Constructor
    TestData()
    {}

    }//End of class ServerTestData.
     
    Richard Maher, Sep 1, 2007
    #3
  4. Richard Maher wrote:
    > Hi,
    >
    > I don't know what is causing the hang but FWIW I use the following Timeouts
    > to put a time limit on my socket connections and socket reads. At least then
    > you be able to identify which read isn't being satisfied and track down what
    > happened to the writer.
    >
    > t3Sock.connect(new InetSocketAddress(host,port), CONTIMOUT);
    >
    > : : :
    >
    > public void setTimeout(int msecs) throws UnknownHostException, IOException
    > {
    > t3Sock.setSoTimeout(msecs);
    > }
    >
    > Cheers Richard Maher


    At least in my case, socket timeout did not work when the hang occurred.

    --

    Knute Johnson
    email s/nospam/knute/
     
    Knute Johnson, Sep 1, 2007
    #4
  5. ILPTAB

    ILPTAB Guest

    On Aug 31, 11:38 pm, Knute Johnson <>
    wrote:
    > Richard Maher wrote:
    > > Hi,

    >
    > > I don't know what is causing the hang but FWIW I use the following Timeouts
    > > to put a time limit on my socket connections and socket reads. At least then
    > > you be able to identify which read isn't being satisfied and track down what
    > > happened to the writer.

    >
    > > t3Sock.connect(new InetSocketAddress(host,port), CONTIMOUT);

    >
    > > : : :

    >
    > > public void setTimeout(int msecs) throws UnknownHostException, IOException
    > > {
    > > t3Sock.setSoTimeout(msecs);
    > > }

    >
    > > Cheers Richard Maher

    >
    > At least in my case, socket timeout did not work when the hang occurred.
    >
    > --
    >
    > Knute Johnson
    > email s/nospam/knute/- Hide quoted text -
    >
    > - Show quoted text -


    It's all back at the office so I haven't really had a chance to test
    it. I wonder if there is a place to post this message on Sun
    MicroSysten's site. I really need to get this fixed.

    Steve Rulison
     
    ILPTAB, Sep 1, 2007
    #5
  6. ILPTAB wrote:
    > On Aug 31, 11:38 pm, Knute Johnson <>
    > wrote:
    >> Richard Maher wrote:
    >>> Hi,
    >>> I don't know what is causing the hang but FWIW I use the following Timeouts
    >>> to put a time limit on my socket connections and socket reads. At least then
    >>> you be able to identify which read isn't being satisfied and track down what
    >>> happened to the writer.
    >>> t3Sock.connect(new InetSocketAddress(host,port), CONTIMOUT);
    >>> : : :
    >>> public void setTimeout(int msecs) throws UnknownHostException, IOException
    >>> {
    >>> t3Sock.setSoTimeout(msecs);
    >>> }
    >>> Cheers Richard Maher

    >> At least in my case, socket timeout did not work when the hang occurred.
    >>
    >> --
    >>
    >> Knute Johnson
    >> email s/nospam/knute/- Hide quoted text -
    >>
    >> - Show quoted text -

    >
    > It's all back at the office so I haven't really had a chance to test
    > it. I wonder if there is a place to post this message on Sun
    > MicroSysten's site. I really need to get this fixed.
    >
    > Steve Rulison
    >


    File a bug at bugs.sun.com. I'll vote for it if you post it.

    --

    Knute Johnson
    email s/nospam/knute/
     
    Knute Johnson, Sep 1, 2007
    #6
  7. ILPTAB wrote:
    > I am currently supporting an interactive web site for a state agency.
    > Recently we started getting reports from SOME of the users that the
    > applet hangs when they attempt to submit data to the servlet running
    > on our web server. We have not made any changes to the java code so
    > the only thing I can figure is that it must be happening as a result
    > of an update to the java JRE or Windows. Note that I said it's
    > occurring with SOME of the users. Other people seem to be having no
    > problem at all with it.
    >
    > To help illustrate the problem, I put together a small test server and
    > applet that demonstrates the problem. I have included the source code
    > for both parts below. On the applet side, it hangs when it comes to a
    > line that attempts to instantiate the ObjectInputStream class and
    > retrieve the input stream from the applet.
    >
    > ObjectInputStream inobj = new ObjectInputStream(s.getInputStream());
    >
    > Since the applet locks up, I am unable to give you any error messages
    > in the java console. In fact the browser gets so locked up that it
    > requires the user to close the session from the Windows task manager.
    >
    > On the Servlet side it hangs at the line that attempts to read the
    > data stream from the socket connection.
    >
    > sSearchField_ = in.readLine();
    >
    > The error messages generated at the server are as follows:
    >
    > Java.lang.NullpointerException at ServerSide.testLookup(ServerSide.54)
    >
    > at ServerSide.run(ServerSide.java.98)
    >
    > at jave.lang.thread.run(Unkown Source)
    >
    >
    > Any help in resolving this problem would be greatly appricated.
    >
    > Thank you.
    >
    >
    >
    > Here is the source code for both the Servlet and the applet.
    >
    >
    > /* Class Name: AppletSide.java
    >
    > Copyright © 2007 Steve Rulison
    >
    > Version 1.0.0
    >
    > Purpose: This java applet will display relevent information
    > pertaining to
    > this examplet
    > */
    >
    > import javax.swing.*;
    > import javax.swing.event.*;
    > import javax.swing.event.ListSelectionListener;
    > import javax.swing.event.ListSelectionEvent;
    > import javax.swing.table.*;
    > import java.awt.*;
    > import java.awt.event.*;
    > import java.applet.*;
    >
    > import java.io.*;
    > import java.util.*;
    > import java.net.*;
    > import java.lang.*;
    >
    > public class AppletSide extends JApplet
    > implements ActionListener, KeyListener, MouseListener, Serializable
    > {
    > private static final long serialVersionUID = 1;
    >
    > private JButton theSubmitButton_, theClearButton_;
    > private Socket s;
    > private String host, ServerName_;
    > private TestData td;
    > private JPanel appletPanel, resultPanel, buttonPanel,
    > socketPanel, headingPanel;
    > private Font f1 = new Font("Sansserf", Font.BOLD, 28);
    >
    > private JLabel socketConnectionLabel = new JLabel("");
    > private JTextField resultField1, resultField2, resultField3,
    > resultField4, resultField5;
    >
    > private java.awt.List inquirylist;
    >
    > //Constructor
    > public AppletSide()
    > {
    > headingPanel = new JPanel();
    > headingPanel.setLayout(new FlowLayout(FlowLayout.CENTER));
    >
    > //Initialize String variables for output.
    > searchSetup();
    > }//Constructor
    >
    > public void init()
    > {
    > // Note: The getCodeBase().getHost() methods must be invoked from
    > the
    > // init() method.
    > ServerName_ = getCodeBase().getHost();
    > System.out.println(ServerName_);
    >
    > System.out.println("Test Applet Version");
    > }//End of init.
    >
    > //Establish a socket connection with the server.
    > private boolean createSocket(String pServerName)
    > {
    > boolean SocketConnectSuccessful = false;
    > try
    > {
    > int iPort = 554;
    > s = new Socket(pServerName, iPort);
    > SocketConnectSuccessful = true;
    > socketConnectionLabel.setText("Socket connection successfully
    > established with host " + pServerName + " on port " + iPort);
    > socketPanel.validate();
    > }
    > catch(Exception e)
    > {
    > e.printStackTrace(System.err);
    > System.out.println(e);
    > SocketConnectSuccessful = false;
    > socketConnectionRefused();
    > }//End of catch block.
    > return SocketConnectSuccessful;
    > }//End of method createSocket.
    >
    > //This method is called when a socket connection could not be
    > established.
    > private void socketConnectionRefused()
    > {
    > socketConnectionLabel.setText("Unable to establish a connection with
    > host. Please contact you network administrator.");
    > socketPanel.validate();
    > }//End of method socketConnectionRefused.
    >
    > //Setup search Inquiry labels.
    > private void searchSetup()
    > {
    > setLayout(new BorderLayout());
    >
    > appletPanel = new JPanel();
    > appletPanel.setLayout(new GridLayout(0,1));
    >
    >
    > JLabel titleLabel = new JLabel("Test Page");
    > titleLabel.setFont(f1);
    > titleLabel.setForeground(Color.black);
    >
    > headingPanel.add(titleLabel);
    > appletPanel.add(headingPanel);
    >
    > JPanel inquiryPanel = new JPanel();
    > inquiryPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
    >
    > JLabel inquiryLabel = new JLabel("Make Selection: ");
    > inquiryPanel.add(inquiryLabel);
    >
    > inquirylist = new java.awt.List();
    > inquirylist.add("Test 1");
    > inquirylist.add("Test 2");
    > inquirylist.add("Test 3");
    > inquirylist.select(0);
    >
    > inquiryPanel.add(inquirylist);
    >
    > appletPanel.add(inquiryPanel);
    >
    > resultSetup();
    >
    > socketPanel = new JPanel();
    > socketPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
    > socketPanel.add(socketConnectionLabel);
    > appletPanel.add(socketPanel);
    >
    >
    > buttonPanel = new JPanel();
    > buttonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));
    >
    > theSubmitButton_ = new JButton("Submit");
    > theSubmitButton_.addActionListener(this);
    > theSubmitButton_.addKeyListener(this);
    >
    > buttonPanel.add(theSubmitButton_);
    > theClearButton_ = new JButton("Clear");
    > theClearButton_.addActionListener(this);
    > theClearButton_.addKeyListener(this);
    > buttonPanel.add(theClearButton_);
    > appletPanel.add(buttonPanel);
    >
    > add(BorderLayout.CENTER, appletPanel);
    >
    > }//End of method searchLabelSetup.
    >
    > //Setup result labels.
    > private void resultSetup()
    > {
    > resultPanel = new JPanel();
    > resultPanel.setLayout(new GridLayout(5,2));
    >
    > JLabel resultLabel1 = new JLabel("Field 1: ", JLabel.RIGHT);
    > JLabel resultLabel2 = new JLabel("Field 2: ", JLabel.RIGHT);
    > JLabel resultLabel3 = new JLabel("Field 3: ", JLabel.RIGHT);
    > JLabel resultLabel4 = new JLabel("Field 4: ", JLabel.RIGHT);
    > JLabel resultLabel5 = new JLabel("Field 5: ", JLabel.RIGHT);
    >
    > resultField1 = new JTextField("Default value 1", 5);
    > resultField1.setEditable(false);
    > resultField2 = new JTextField("Default value 2 ",5);
    > resultField2.setEditable(false);
    > resultField3 = new JTextField("Default value 3",5);
    > resultField3.setEditable(false);
    > resultField4 = new JTextField("Default value 4",5);
    > resultField4.setEditable(false);
    > resultField5 = new JTextField("Default value 5",5);
    > resultField5.setEditable(false);
    >
    > resultPanel.add(resultLabel1);
    > resultPanel.add(resultField1);
    > resultPanel.add(resultLabel2);
    > resultPanel.add(resultField2);
    > resultPanel.add(resultLabel3);
    > resultPanel.add(resultField3);
    > resultPanel.add(resultLabel4);
    > resultPanel.add(resultField4);
    > resultPanel.add(resultLabel5);
    > resultPanel.add(resultField5);
    >
    > appletPanel.add(resultPanel);
    >
    > }//End of method resultLabelSetup.
    >
    > // Display the fields that have been populated with data received
    > from the
    > // server application.
    > private void displayResults()
    > {
    > resultField1.setText(td.sField_1);
    > resultField2.setText(td.sField_2);
    > resultField3.setText(td.sField_3);
    > resultField4.setText(td.sField_4);
    > resultField5.setText(td.sField_5);
    > resultPanel.validate();
    > }//End of method displayResults.
    >
    > //Clears fields of data
    > private void clearFields()
    > {
    > resultField1.setText("Default value 1");
    > resultField2.setText("Default value 2");
    > resultField3.setText("Default value 3");
    > resultField4.setText("Default value 4");
    > resultField5.setText("Default value 5");
    > resultPanel.validate();
    > inquirylist.select(0);
    > }//End of method clearFields.
    >
    > //Reset the applet to allow the user to perform a new search.
    > private void resetSearch()
    > {
    > this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
    > clearFields();
    > createSocket(ServerName_);
    > this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
    > }//End of method resetSearch.
    >
    > //Perform Input/Output operations with the server.
    > private void serverIO()
    > {
    > this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
    >
    > try
    > {
    > PrintWriter out =
    > new PrintWriter(
    > new BufferedWriter(
    > new OutputStreamWriter(
    > s.getOutputStream())),true);
    >
    >
    > System.out.println("Check point 1 @ serverIO method.");
    > out.println(inquirylist.getItem(inquirylist.getSelectedIndex()));
    > // Thread.currentThread().sleep(5000);
    > System.out.println("Check point 2 @ serverIO method.");
    > //Read data back from server - Inputstream
    > ObjectInputStream inObj = new
    > ObjectInputStream(s.getInputStream());
    > System.out.println("Check point 3 @ serverIO method.");
    > out.flush();
    > System.out.println("Check point 4 @ serverIO method.");
    >
    > td = (TestData) inObj.readObject();
    >
    > s.close();
    > if(td.bRecFound)
    > displayResults();
    > else
    > resetSearch();
    > }
    > catch(Exception e)
    > {
    > System.out.println("Check point 1 - Exception: " + e);
    >
    > }//End of try/catch block
    >
    > this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
    > }//End of method ServerIO
    >
    >
    > //Event handling method.
    > public void actionPerformed(ActionEvent evt)
    > {
    > if(evt.getSource() == theClearButton_)
    > {
    > clearFields();
    > repaint();
    > }
    > else if(evt.getSource() == theSubmitButton_)
    > {
    > if(createSocket(ServerName_))
    > {
    > System.getSecurityManager();
    >
    > // searchLabelSetup();
    > validate();
    > System.out.println(s.getInetAddress());
    > serverIO();
    > repaint();
    > }
    > else
    > socketConnectionRefused();
    > }
    > }//End of method actionPerformed
    >
    >
    > //Methodsfor handling for keyboard events
    > public void keyPressed(KeyEvent evt){}
    > public void keyReleased(KeyEvent evt){}
    > public void keyTyped(KeyEvent evt)
    > {
    > // System.out.println(" " + (int)evt.getKeyChar() );
    >
    > if(evt.getSource() == theClearButton_)
    > {
    > clearFields();
    > repaint();
    > }
    > else if(evt.getSource() == theSubmitButton_)
    > {
    > serverIO();
    > repaint();
    > }
    > }//End of method keyTyped.
    >
    > public void mouseClicked(MouseEvent evt)
    > {
    > if(evt.getClickCount() == 2)
    > {
    > }
    > }
    > public void mouseExited(MouseEvent event){}
    > public void mouseEntered(MouseEvent event){}
    > public void mouseReleased(MouseEvent event){}
    > public void mousePressed(MouseEvent event){}
    >
    > }//End of class ApplSide.
    >
    > class TestData implements Serializable
    > {
    > private static final long serialVersionUID = 1;
    >
    > /* Test Data */
    > public String sField_1, sField_2, sField_3, sField_4, sField_5;
    > public boolean bRecFound;
    >
    > //Constructor
    > TestData()
    > {}
    > }//End of class ServerTestData.
    >
    > - - - - - - - - - - - - - - - - -
    > - - - -
    >
    > /* Class name: ServerSide
    >
    > Author: Steven Rulison
    >
    > Purpose: Demonstrate the servlet side
    > */
    >
    > import java.io.*;
    > import java.util.*;
    > import java.net.*;
    >
    > public class ServerSide extends Thread
    > {
    > private TestData td;
    > private Socket s;
    > private String sSearchField_;
    >
    > public static void main(String[] Args)
    > {
    > try
    > {
    > ServerSocket ss = new ServerSocket(554);
    >
    > int spawnCnt = 0;
    > while(true)
    > {
    > Socket s = ss.accept();
    >
    > ++spawnCnt;
    > System.out.println("Spawning " + spawnCnt);
    >
    >
    > Thread servSide = new Thread(new ServerSide(s), "serverside");
    > servSide.start();
    > }
    > }catch(IOException e)
    > {
    > e.printStackTrace(System.err);
    > }
    > }//End of main.
    >
    >
    > //Constructor.
    > public ServerSide(Socket s_)
    > {
    > s = s_;
    > }//End of Constructor.
    >
    >
    > private void testLookup(String sSearch)
    > {
    > td = new TestData();
    > td.bRecFound = true;
    > if(sSearch.trim().equals("Test 1"))
    > {
    > td.sField_1 = "Alpha";
    > td.sField_2 = "Beta";
    > td.sField_3 = "Gamma";
    > td.sField_4 = "Delta";
    > td.sField_5 = "Epsilon";
    > }
    > else if(sSearch.trim().equals("Test 2"))
    > {
    > td.sField_1 = "AAA";
    > td.sField_2 = "BBB";
    > td.sField_3 = "CCC";
    > td.sField_4 = "DDDD";
    > td.sField_5 = "EEEE";
    > }
    > else if(sSearch.trim().equals("Test 3"))
    > {
    > td.sField_1 = "111";
    > td.sField_2 = "222";
    > td.sField_3 = "333";
    > td.sField_4 = "444";
    > td.sField_5 = "555";
    > }
    > }// End of method testLookup.
    >
    > public void run()
    > {
    > try
    > {
    > //Setup Input Stream.
    > BufferedReader in =
    > new BufferedReader( new InputStreamReader(s.getInputStream()));
    >
    > // Setup output Stream.
    > ObjectOutputStream ObjOut = new
    > ObjectOutputStream(s.get());
    >
    > //Perform intial read...
    > sSearchField_ = in.readLine();
    >
    > Thread.currentThread().sleep(5000);
    >
    > System.out.println("The sSearchField_ variable = " + sSearchField_);
    >
    > testLookup(sSearchField_);
    >
    > ObjOut.writeObject(td);
    > ObjOut.flush();
    > ObjOut.close();
    >
    > s.close();
    > }
    > catch(Exception e)
    > {
    > e.printStackTrace(System.err);
    > }
    > }//End of run method
    > }//End of ServerSide class...
    >
    >
    > /*
    > This is the class template that will be used to create the object
    > that will
    > be passed through to the ObjectInput/Output - stream to the lookup
    > applet.
    > */
    > class TestData implements Serializable
    > {
    > private static final long serialVersionUID = 1;
    >
    > /* Test Data */
    > public String sField_1, sField_2, sField_3, sField_4, sField_5;
    > public boolean bRecFound;
    >
    > //Constructor
    > TestData()
    > {}
    >
    > }//End of class ServerTestData.
    >


    I may have done you a bad turn here. I think your problem is because
    you aren't creating an ObjectOutputStream on the socket before you
    create your ObjectInputStream. I think they have to be matched (at
    least if you are going to do input) on the socket and the
    ObjectOutputStream has to be created first. This is a known source of
    hangs. I was too hasty reading your post the first time.

    --

    Knute Johnson
    email s/nospam/knute/
     
    Knute Johnson, Sep 3, 2007
    #7
  8. ILPTAB

    ILPTAB Guest

    On Sep 2, 11:16 pm, Knute Johnson <>
    wrote:
    > ILPTAB wrote:
    > > I am currently supporting an interactive web site for a state agency.
    > > Recently we started getting reports from SOME of the users that the
    > > applet hangs when they attempt to submit data to the servlet running
    > > on our web server. We have not made any changes to the java code so
    > > the only thing I can figure is that it must be happening as a result
    > > of an update to the java JRE or Windows. Note that I said it's
    > > occurring with SOME of the users. Other people seem to be having no
    > > problem at all with it.

    >
    > > To help illustrate the problem, I put together a small test server and
    > > applet that demonstrates the problem. I have included the source code
    > > for both parts below. On the applet side, it hangs when it comes to a
    > > line that attempts to instantiate the ObjectInputStream class and
    > > retrieve the input stream from the applet.

    >
    > > ObjectInputStream inobj = new ObjectInputStream(s.getInputStream());

    >
    > > Since the applet locks up, I am unable to give you any error messages
    > > in the java console. In fact the browser gets so locked up that it
    > > requires the user to close the session from the Windows task manager.

    >
    > > On the Servlet side it hangs at the line that attempts to read the
    > > data stream from the socket connection.

    >
    > > sSearchField_ = in.readLine();

    >
    > > The error messages generated at the server are as follows:

    >
    > > Java.lang.NullpointerException at ServerSide.testLookup(ServerSide.54)

    >
    > > at ServerSide.run(ServerSide.java.98)

    >
    > > at jave.lang.thread.run(Unkown Source)

    >
    > > Any help in resolving this problem would be greatly appricated.

    >
    > > Thank you.

    >
    > > Here is the source code for both the Servlet and the applet.

    >
    > > /* Class Name: AppletSide.java

    >
    > > Copyright © 2007 Steve Rulison

    >
    > > Version 1.0.0

    >
    > > Purpose: This java applet will display relevent information
    > > pertaining to
    > > this examplet
    > > */

    >
    > > import javax.swing.*;
    > > import javax.swing.event.*;
    > > import javax.swing.event.ListSelectionListener;
    > > import javax.swing.event.ListSelectionEvent;
    > > import javax.swing.table.*;
    > > import java.awt.*;
    > > import java.awt.event.*;
    > > import java.applet.*;

    >
    > > import java.io.*;
    > > import java.util.*;
    > > import java.net.*;
    > > import java.lang.*;

    >
    > > public class AppletSide extends JApplet
    > > implements ActionListener, KeyListener, MouseListener, Serializable
    > > {
    > > private static final long serialVersionUID = 1;

    >
    > > private JButton theSubmitButton_, theClearButton_;
    > > private Socket s;
    > > private String host, ServerName_;
    > > private TestData td;
    > > private JPanel appletPanel, resultPanel, buttonPanel,
    > > socketPanel, headingPanel;
    > > private Font f1 = new Font("Sansserf", Font.BOLD, 28);

    >
    > > private JLabel socketConnectionLabel = new JLabel("");
    > > private JTextField resultField1, resultField2, resultField3,
    > > resultField4, resultField5;

    >
    > > private java.awt.List inquirylist;

    >
    > > //Constructor
    > > public AppletSide()
    > > {
    > > headingPanel = new JPanel();
    > > headingPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

    >
    > > //Initialize String variables for output.
    > > searchSetup();
    > > }//Constructor

    >
    > > public void init()
    > > {
    > > // Note: The getCodeBase().getHost() methods must be invoked from
    > > the
    > > // init() method.
    > > ServerName_ = getCodeBase().getHost();
    > > System.out.println(ServerName_);

    >
    > > System.out.println("Test Applet Version");
    > > }//End of init.

    >
    > > //Establish a socket connection with the server.
    > > private boolean createSocket(String pServerName)
    > > {
    > > boolean SocketConnectSuccessful = false;
    > > try
    > > {
    > > int iPort = 554;
    > > s = new Socket(pServerName, iPort);
    > > SocketConnectSuccessful = true;
    > > socketConnectionLabel.setText("Socket connection successfully
    > > established with host " + pServerName + " on port " + iPort);
    > > socketPanel.validate();
    > > }
    > > catch(Exception e)
    > > {
    > > e.printStackTrace(System.err);
    > > System.out.println(e);
    > > SocketConnectSuccessful = false;
    > > socketConnectionRefused();
    > > }//End of catch block.
    > > return SocketConnectSuccessful;
    > > }//End of method createSocket.

    >
    > > //This method is called when a socket connection could not be
    > > established.
    > > private void socketConnectionRefused()
    > > {
    > > socketConnectionLabel.setText("Unable to establish a connection with
    > > host. Please contact you network administrator.");
    > > socketPanel.validate();
    > > }//End of method socketConnectionRefused.

    >
    > > //Setup search Inquiry labels.
    > > private void searchSetup()
    > > {
    > > setLayout(new BorderLayout());

    >
    > > appletPanel = new JPanel();
    > > appletPanel.setLayout(new GridLayout(0,1));

    >
    > > JLabel titleLabel = new JLabel("Test Page");
    > > titleLabel.setFont(f1);
    > > titleLabel.setForeground(Color.black);

    >
    > > headingPanel.add(titleLabel);
    > > appletPanel.add(headingPanel);

    >
    > > JPanel inquiryPanel = new JPanel();
    > > inquiryPanel.setLayout(new FlowLayout(FlowLayout.LEFT));

    >
    > > JLabel inquiryLabel = new JLabel("Make Selection: ");
    > > inquiryPanel.add(inquiryLabel);

    >
    > > inquirylist = new java.awt.List();
    > > inquirylist.add("Test 1");
    > > inquirylist.add("Test 2");
    > > inquirylist.add("Test 3");
    > > inquirylist.select(0);

    >
    > > inquiryPanel.add(inquirylist);

    >
    > > appletPanel.add(inquiryPanel);

    >
    > > resultSetup();

    >
    > > socketPanel = new JPanel();
    > > socketPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
    > > socketPanel.add(socketConnectionLabel);
    > > appletPanel.add(socketPanel);

    >
    > > buttonPanel = new JPanel();
    > > buttonPanel.setLayout(new FlowLayout(FlowLayout.CENTER));

    >
    > > theSubmitButton_ = new JButton("Submit");
    > > theSubmitButton_.addActionListener(this);
    > > theSubmitButton_.addKeyListener(this);

    >
    > > buttonPanel.add(theSubmitButton_);
    > > theClearButton_ = new JButton("Clear");
    > > theClearButton_.addActionListener(this);
    > > theClearButton_.addKeyListener(this);
    > > buttonPanel.add(theClearButton_);
    > > appletPanel.add(buttonPanel);

    >
    > > add(BorderLayout.CENTER, appletPanel);

    >
    > > }//End of method searchLabelSetup.

    >
    > > //Setup result labels.
    > > private void resultSetup()
    > > {
    > > resultPanel = new JPanel();
    > > resultPanel.setLayout(new GridLayout(5,2));

    >
    > > JLabel resultLabel1 = new JLabel("Field 1: ", JLabel.RIGHT);
    > > JLabel resultLabel2 = new JLabel("Field 2: ", JLabel.RIGHT);
    > > JLabel resultLabel3 = new JLabel("Field 3: ", JLabel.RIGHT);
    > > JLabel resultLabel4 = new JLabel("Field 4: ", JLabel.RIGHT);
    > > JLabel resultLabel5 = new JLabel("Field 5: ", JLabel.RIGHT);

    >
    > > resultField1 = new JTextField("Default value 1", 5);
    > > resultField1.setEditable(false);
    > > resultField2 = new JTextField("Default value 2 ",5);
    > > resultField2.setEditable(false);
    > > resultField3 = new JTextField("Default value 3",5);
    > > resultField3.setEditable(false);
    > > resultField4 = new JTextField("Default value 4",5);
    > > resultField4.setEditable(false);
    > > resultField5 = new JTextField("Default value 5",5);
    > > resultField5.setEditable(false);

    >
    > > resultPanel.add(resultLabel1);
    > > resultPanel.add(resultField1);
    > > resultPanel.add(resultLabel2);
    > > resultPanel.add(resultField2);
    > > resultPanel.add(resultLabel3);
    > > resultPanel.add(resultField3);
    > > resultPanel.add(resultLabel4);
    > > resultPanel.add(resultField4);
    > > resultPanel.add(resultLabel5);
    > > resultPanel.add(resultField5);

    >
    > > appletPanel.add(resultPanel);

    >
    > > }//End of method resultLabelSetup.

    >
    > > // Display the fields that have been populated with data received
    > > from the
    > > // server application.
    > > private void displayResults()
    > > {
    > > resultField1.setText(td.sField_1);
    > > resultField2.setText(td.sField_2);
    > > resultField3.setText(td.sField_3);
    > > resultField4.setText(td.sField_4);
    > > resultField5.setText(td.sField_5);
    > > resultPanel.validate();
    > > }//End of method displayResults.

    >
    > > //Clears fields of data
    > > private void clearFields()
    > > {
    > > resultField1.setText("Default value 1");
    > > resultField2.setText("Default value 2");
    > > resultField3.setText("Default value 3");
    > > resultField4.setText("Default value 4");
    > > resultField5.setText("Default value 5");
    > > resultPanel.validate();
    > > inquirylist.select(0);
    > > }//End of method clearFields.

    >
    > > //Reset the applet to allow the user to perform a new search.
    > > private void resetSearch()
    > > {
    > > this.setCursor(new Cursor(Cursor.WAIT_CURSOR));
    > > clearFields();
    > > createSocket(ServerName_);
    > > this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
    > > }//End of method resetSearch.

    >
    > > //Perform Input/Output operations with the server.
    > > private void serverIO()
    > > {
    > > this.setCursor(new Cursor(Cursor.WAIT_CURSOR));

    >
    > > try
    > > {
    > > PrintWriter out =
    > > new PrintWriter(
    > > new BufferedWriter(
    > > new OutputStreamWriter(
    > > s.getOutputStream())),true);

    >
    > > System.out.println("Check point 1 @ serverIO method.");
    > > out.println(inquirylist.getItem(inquirylist.getSelectedIndex()));
    > > // Thread.currentThread().sleep(5000);
    > > System.out.println("Check point 2 @ serverIO method.");
    > > //Read data back from server - Inputstream
    > > ObjectInputStream inObj = new
    > > ObjectInputStream(s.getInputStream());
    > > System.out.println("Check point 3 @ serverIO method.");
    > > out.flush();
    > > System.out.println("Check point 4 @ serverIO method.");

    >
    > > td = (TestData) inObj.readObject();

    >
    > > s.close();
    > > if(td.bRecFound)
    > > displayResults();
    > > else
    > > resetSearch();
    > > }
    > > catch(Exception e)
    > > {
    > > System.out.println("Check point 1 - Exception: " + e);

    >
    > > }//End of try/catch block

    >
    > > this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
    > > }//End of method ServerIO

    >
    > > //Event handling method.
    > > public void actionPerformed(ActionEvent evt)
    > > {
    > > if(evt.getSource() == theClearButton_)
    > > {
    > > clearFields();
    > > repaint();
    > > }
    > > else if(evt.getSource() == theSubmitButton_)
    > > {
    > > if(createSocket(ServerName_))
    > > {
    > > System.getSecurityManager();

    >
    > > // searchLabelSetup();
    > > validate();
    > > System.out.println(s.getInetAddress());
    > > serverIO();
    > > repaint();
    > > }
    > > else
    > > socketConnectionRefused();
    > > }
    > > }//End of method actionPerformed

    >
    > > //Methodsfor handling for keyboard events
    > > public void keyPressed(KeyEvent evt){}
    > > public void keyReleased(KeyEvent evt){}
    > > public void keyTyped(KeyEvent evt)
    > > {
    > > // System.out.println(" " + (int)evt.getKeyChar() );

    >
    > > if(evt.getSource() == theClearButton_)
    > > {
    > > clearFields();
    > > repaint();
    > > }
    > > else if(evt.getSource() == theSubmitButton_)
    > > {
    > > serverIO();
    > > repaint();
    > > }
    > > }//End of method keyTyped.

    >
    > > public void mouseClicked(MouseEvent evt)
    > > {
    > > if(evt.getClickCount() == 2)
    > > {
    > > }
    > > }
    > > public void mouseExited(MouseEvent event){}
    > > public void mouseEntered(MouseEvent event){}
    > > public void mouseReleased(MouseEvent event){}
    > > public void mousePressed(MouseEvent event){}

    >
    > > }//End of class ApplSide.

    >
    > > class TestData implements Serializable
    > > {
    > > private static final long serialVersionUID = 1;

    >
    > > /* Test Data */
    > > public String sField_1, sField_2, sField_3, sField_4, sField_5;
    > > public boolean bRecFound;

    >
    > > //Constructor
    > > TestData()
    > > {}
    > > }//End of class ServerTestData.

    >
    > > - - - - - - - - - - - - - - - - -
    > > - - - -

    >
    > > /* Class name: ServerSide

    >
    > > Author: Steven Rulison

    >
    > > Purpose: Demonstrate the servlet side
    > > */

    >
    > > import java.io.*;
    > > import java.util.*;
    > > import java.net.*;

    >
    > > public class ServerSide extends Thread
    > > {
    > > private TestData td;
    > > private Socket s;
    > > private String sSearchField_;

    >
    > > public static void main(String[] Args)
    > > {
    > > try
    > > {
    > > ServerSocket ss = new ServerSocket(554);

    >
    > > int spawnCnt = 0;
    > > while(true)
    > > {
    > > Socket s = ss.accept();

    >
    > > ++spawnCnt;
    > > System.out.println("Spawning " + spawnCnt);

    >
    > > Thread servSide = new Thread(new ServerSide(s), "serverside");
    > > servSide.start();
    > > }
    > > }catch(IOException e)
    > > {
    > > e.printStackTrace(System.err);
    > > }
    > > }//End of main.

    >
    > > //Constructor.
    > > public ServerSide(Socket s_)
    > > {
    > > s = s_;
    > > }//End of Constructor.

    >
    > > private void testLookup(String sSearch)
    > > {
    > > td = new TestData();
    > > td.bRecFound = true;
    > > if(sSearch.trim().equals("Test 1"))
    > > {
    > > td.sField_1 = "Alpha";
    > > td.sField_2 = "Beta";
    > > td.sField_3 = "Gamma";
    > > td.sField_4 = "Delta";
    > > td.sField_5 = "Epsilon";
    > > }
    > > else if(sSearch.trim().equals("Test 2"))
    > > {
    > > td.sField_1 = "AAA";
    > > td.sField_2 = "BBB";
    > > td.sField_3 = "CCC";
    > > td.sField_4 = "DDDD";
    > > td.sField_5 = "EEEE";
    > > }
    > > else if(sSearch.trim().equals("Test 3"))
    > > {
    > > td.sField_1 = "111";
    > > td.sField_2 = "222";
    > > td.sField_3 = "333";
    > > td.sField_4 = "444";
    > > td.sField_5 = "555";
    > > }
    > > }// End of method testLookup.

    >
    > > public void run()
    > > {
    > > try
    > > {
    > > //Setup Input Stream.
    > > BufferedReader in =
    > > new BufferedReader( new InputStreamReader(s.getInputStream()));

    >
    > > // Setup output Stream.
    > > ObjectOutputStream ObjOut = new
    > > ObjectOutputStream(s.get());

    >
    > > //Perform intial read...
    > > sSearchField_ = in.readLine();

    >
    > > Thread.currentThread().sleep(5000);

    >
    > > System.out.println("The sSearchField_ variable = " + sSearchField_);

    >
    > > testLookup(sSearchField_);

    >
    > > ObjOut.writeObject(td);
    > > ObjOut.flush();
    > > ObjOut.close();

    >
    > > s.close();
    > > }
    > > catch(Exception e)
    > > {
    > > e.printStackTrace(System.err);
    > > }
    > > }//End of run method
    > > }//End of ServerSide class...

    >
    > > /*
    > > This is the class template that will be used to create the object
    > > that will
    > > be passed through to the ObjectInput/Output - stream to the lookup
    > > applet.
    > > */
    > > class TestData implements Serializable
    > > {
    > > private static final long serialVersionUID = 1;

    >
    > > /* Test Data */
    > > public String sField_1, sField_2, sField_3, sField_4, sField_5;
    > > public boolean bRecFound;

    >
    > > //Constructor
    > > TestData()
    > > {}

    >
    > > }//End of class ServerTestData.

    >
    > I may have done you a bad turn here. I think your problem is because
    > you aren't creating an ObjectOutputStream on the socket before you
    > create your ObjectInputStream. I think they have to be matched (at
    > least if you are going to do input) on the socket and the
    > ObjectOutputStream has to be created first. This is a known source of
    > hangs. I was too hasty reading your post the first time.
    >
    > --
    >
    > Knute Johnson
    > email s/nospam/knute/


    Interesting. I will look into it. The only thing is, it dosen't do
    it consistanntly. The applet hangs for some people amd not on
    others. Never the less, I will make the changes you suggested and see
    how that works. Thanks for you imput.

    Steve R.
     
    ILPTAB, Sep 4, 2007
    #8
  9. ILPTAB wrote:
    >> I may have done you a bad turn here. I think your problem is because
    >> you aren't creating an ObjectOutputStream on the socket before you
    >> create your ObjectInputStream. I think they have to be matched (at
    >> least if you are going to do input) on the socket and the
    >> ObjectOutputStream has to be created first. This is a known source of
    >> hangs. I was too hasty reading your post the first time.
    >>
    >> --
    >>
    >> Knute Johnson
    >> email s/nospam/knute/

    >
    > Interesting. I will look into it. The only thing is, it dosen't do
    > it consistanntly. The applet hangs for some people amd not on
    > others. Never the less, I will make the changes you suggested and see
    > how that works. Thanks for you imput.
    >
    > Steve R.


    Steve:

    Sorry I didn't look at it more closely when you first posted. It
    sounded just like the problem I'm having. Please post here if you get
    it to work.

    --

    Knute Johnson
    email s/nospam/knute/
     
    Knute Johnson, Sep 4, 2007
    #9
  10. ILPTAB

    Roedy Green Guest

    On Fri, 31 Aug 2007 21:49:56 -0000, ILPTAB <> wrote,
    quoted or indirectly quoted someone who said :

    >
    >Any help in resolving this problem would be greatly appricated.


    I would put a version number in the Applet and SerialVersionUIDs on
    all transported classes. Have the applet display its version number
    first thing so you can be sure you are getting a fresh copy, not
    something in cache.

    Further I would put a Long as the first item in the stream; it is a
    stream version number. It might just be a serialVersionUID of an
    important class. Read and compare and if it does not match, bitch up
    front rather than getting into some corner that hangs you.
    --
    Roedy Green Canadian Mind Products
    The Java Glossary
    http://mindprod.com
     
    Roedy Green, Sep 4, 2007
    #10
  11. ILPTAB

    Nigel Wade Guest

    ILPTAB wrote:

    > I am currently supporting an interactive web site for a state agency.
    > Recently we started getting reports from SOME of the users that the
    > applet hangs when they attempt to submit data to the servlet running
    > on our web server. We have not made any changes to the java code so
    > the only thing I can figure is that it must be happening as a result
    > of an update to the java JRE or Windows. Note that I said it's
    > occurring with SOME of the users. Other people seem to be having no
    > problem at all with it.
    >
    > To help illustrate the problem, I put together a small test server and
    > applet that demonstrates the problem. I have included the source code
    > for both parts below. On the applet side, it hangs when it comes to a
    > line that attempts to instantiate the ObjectInputStream class and
    > retrieve the input stream from the applet.
    >
    > ObjectInputStream inobj = new ObjectInputStream(s.getInputStream());
    >
    > Since the applet locks up, I am unable to give you any error messages
    > in the java console. In fact the browser gets so locked up that it
    > requires the user to close the session from the Windows task manager.
    >
    > On the Servlet side it hangs at the line that attempts to read the
    > data stream from the socket connection.
    >
    > sSearchField_ = in.readLine();
    >
    > The error messages generated at the server are as follows:
    >
    > Java.lang.NullpointerException at ServerSide.testLookup(ServerSide.54)
    >
    > at ServerSide.run(ServerSide.java.98)
    >
    > at jave.lang.thread.run(Unkown Source)
    >
    >
    > Any help in resolving this problem would be greatly appricated.
    >
    > Thank you.
    >
    >


    There may be a potential for a dead-lock situation in your input/output streams,
    with the establishment of the ObjectOutputStream/ObjectInputStream.

    Creating an ObjectOutputStream writes the stream header, and if this isn't
    flushed the client may block in its ObjectInputStream constructor. Try adding a
    flush() to the server ObjectOutputStream immediately after it's opened, before
    reading the request from the client. The client ObjectInputStream constructor
    might block reading the stream header which the server hasn't flushed.

    Also, flushing the client PrintWriter *before* attempting to create the
    ObjectInputStream might release the dead-lock. The server could be blocked
    reading the request, so it hasn't got around to sending the response. If the
    client request is flushed the server could complete reading the request and
    send the response, thus effectively flushing the server ObjectOutputStream
    stream header and releasing the client ObjectInputStream constructor.

    --
    Nigel Wade, System Administrator, Space Plasma Physics Group,
    University of Leicester, Leicester, LE1 7RH, UK
    E-mail :
    Phone : +44 (0)116 2523548, Fax : +44 (0)116 2523555
     
    Nigel Wade, Sep 4, 2007
    #11
  12. Hi Knute,

    > > At least in my case, socket timeout did not work when the hang occurred.


    Sorry I never saw your reply until Steve quoted it in his subsequent reply.

    I do recall your thread, but it did go on for some time and I can't remember
    the outcome; I'd genuinely like to know so if you'd care to post the
    reader's digest version here that'd be great!

    I use the timeout a lot with quasi-polling and dickie-server detection and
    (to date) have not had a problem. Was yours server-death or unresponsiveness
    that led to the timeout not occuring? I've used it with IP stacks that
    do/don't support full_duplex_close and still haven't had a problem.

    Cheers Richard Maher

    "ILPTAB" <> wrote in message
    news:...
    > On Aug 31, 11:38 pm, Knute Johnson <>
    > wrote:
    > > Richard Maher wrote:
    > > > Hi,

    > >
    > > > I don't know what is causing the hang but FWIW I use the following

    Timeouts
    > > > to put a time limit on my socket connections and socket reads. At

    least then
    > > > you be able to identify which read isn't being satisfied and track

    down what
    > > > happened to the writer.

    > >
    > > > t3Sock.connect(new InetSocketAddress(host,port), CONTIMOUT);

    > >
    > > > : : :

    > >
    > > > public void setTimeout(int msecs) throws UnknownHostException,

    IOException
    > > > {
    > > > t3Sock.setSoTimeout(msecs);
    > > > }

    > >
    > > > Cheers Richard Maher

    > >
    > > At least in my case, socket timeout did not work when the hang occurred.
    > >
    > > --
    > >
    > > Knute Johnson
    > > email s/nospam/knute/- Hide quoted text -
    > >
    > > - Show quoted text -

    >
    > It's all back at the office so I haven't really had a chance to test
    > it. I wonder if there is a place to post this message on Sun
    > MicroSysten's site. I really need to get this fixed.
    >
    > Steve Rulison
    >
    >
     
    Richard Maher, Sep 4, 2007
    #12
  13. ILPTAB

    ILPTAB Guest

    On Sep 4, 4:14 am, Nigel Wade <> wrote:
    > ILPTAB wrote:
    > > I am currently supporting an interactive web site for a state agency.
    > > Recently we started getting reports from SOME of the users that the
    > >applethangswhen they attempt to submit data to the servlet running
    > > on our web server. We have not made any changes to the java code so
    > > the only thing I can figure is that it must be happening as a result
    > > of an update to the java JRE or Windows. Note that I said it's
    > > occurring with SOME of the users. Other people seem to be having no
    > > problem at all with it.

    >
    > > To help illustrate the problem, I put together a small test server and
    > >appletthat demonstrates the problem. I have included the source code
    > > for both parts below. On theappletside, ithangswhen it comes to a
    > > line that attempts to instantiate the ObjectInputStream class and
    > > retrieve the input stream from theapplet.

    >
    > > ObjectInputStream inobj = new ObjectInputStream(s.getInputStream());

    >
    > > Since theappletlocks up, I am unable to give you any error messages
    > > in the java console. In fact the browser gets so locked up that it
    > > requires the user to close the session from the Windows task manager.

    >
    > > On the Servlet side ithangsat the line that attempts to read the
    > > data stream from the socket connection.

    >
    > > sSearchField_ = in.readLine();

    >
    > > The error messages generated at the server are as follows:

    >
    > > Java.lang.NullpointerException at ServerSide.testLookup(ServerSide.54)

    >
    > > at ServerSide.run(ServerSide.java.98)

    >
    > > at jave.lang.thread.run(Unkown Source)

    >
    > > Any help in resolving this problem would be greatly appricated.

    >
    > > Thank you.

    >
    > There may be a potential for a dead-lock situation in your input/output streams,
    > with the establishment of the ObjectOutputStream/ObjectInputStream.
    >
    > Creating an ObjectOutputStream writes the stream header, and if this isn't
    > flushed the client may block in its ObjectInputStream constructor. Try adding a
    > flush() to the server ObjectOutputStream immediately after it's opened, before
    > reading the request from the client. The client ObjectInputStream constructor
    > might block reading the stream header which the server hasn't flushed.
    >
    > Also, flushing the client PrintWriter *before* attempting to create the
    > ObjectInputStream might release the dead-lock. The server could be blocked
    > reading the request, so it hasn't got around to sending the response. If the
    > client request is flushed the server could complete reading the request and
    > send the response, thus effectively flushing the server ObjectOutputStream
    > stream header and releasing the client ObjectInputStream constructor.
    >
    > --
    > Nigel Wade, System Administrator, Space Plasma Physics Group,
    > University of Leicester, Leicester, LE1 7RH, UK
    > E-mail :
    > Phone : +44 (0)116 2523548, Fax : +44 (0)116 2523555- Hide quoted text -
    >
    > - Show quoted text -


    To everybody that has responded to my post, I want to thank you for
    your input. I'm really getting some great suggestions here but
    unfortunatly, I am in class all this week and will probably not be
    able to get back to this problem until early next week. At that time
    I am looking forward to trying these suggestions. I just didn't want
    anybody to think that I had lost interest in this.

    Thank you all again.

    Steve.
     
    ILPTAB, Sep 4, 2007
    #13
  14. My problem is a true hang in socket stream I/O. It won't timeout and I
    can't close the socket and get it to throw an exception. It's just
    hung. The most annoying part about it is I can't duplicate it.

    That's it in a nutshell.

    --

    Knute Johnson
    email s/nospam/knute/
     
    Knute Johnson, Sep 5, 2007
    #14
  15. ILPTAB

    ILPTAB Guest

    Update:
    Well I finally got around to trying Nigel's suggestion of calling the
    flush() method after the ObjectOutputStream is opened. Unfortunately
    this did not resolve the problem.

    Can anybody think of a reason why this problem would occur on some
    computers and not on others? I know that Roedy suggested that there
    may be an issue with the version of a class that has been cached into
    the windows browser but the code I posted above was compiled and
    published to our web server exactly one time. How could there be a
    version conflict with that? That being said I will start adding the
    version info to code just in case.

    I just find it so darn perplexing that the site works for some people
    and not for others.

    Could this be a FIREWALL issue?

    Steve Rulison.
     
    ILPTAB, Sep 25, 2007
    #15
  16. ILPTAB

    Roedy Green Guest

    On Tue, 25 Sep 2007 17:07:29 -0000, ILPTAB <> wrote,
    quoted or indirectly quoted someone who said :

    >Could this be a FIREWALL issue?


    Get a sniffer, e.g. Wireshark, http://mindprod.com/jgloss/sniffer.html
    and watch the traffic to see what is happening.

    Use my HTTP class to do the GET/POST. Dump every byte (not char) as
    you get it to futher help figure what is happening.

    You may want some sort of timeout like I have in HTTP.

    See http://mindprod.com/products1.html#HTTP

    You can also instrument your server app to log every byte it receives
    and sends to that Applet.
    --
    Roedy Green Canadian Mind Products
    The Java Glossary
    http://mindprod.com
     
    Roedy Green, Sep 28, 2007
    #16
  17. ILPTAB

    Nigel Wade Guest

    ILPTAB wrote:

    > Update:
    > Well I finally got around to trying Nigel's suggestion of calling the
    > flush() method after the ObjectOutputStream is opened. Unfortunately
    > this did not resolve the problem.
    >
    > Can anybody think of a reason why this problem would occur on some
    > computers and not on others? I know that Roedy suggested that there
    > may be an issue with the version of a class that has been cached into
    > the windows browser but the code I posted above was compiled and
    > published to our web server exactly one time. How could there be a
    > version conflict with that? That being said I will start adding the
    > version info to code just in case.
    >
    > I just find it so darn perplexing that the site works for some people
    > and not for others.


    Is there anything in common with the clients which fail? Windows patch level,
    JRE version, browser etc. I'd go with Roedy's suggestion and use Wireshark to
    look at the packets on the wire to see what's being sent between the applet and
    the server.

    >
    > Could this be a FIREWALL issue?


    I doubt it, unless it's a badly broken firewall. I don't see how a properly
    functioning firewall could result in that scenario.


    --
    Nigel Wade, System Administrator, Space Plasma Physics Group,
    University of Leicester, Leicester, LE1 7RH, UK
    E-mail :
    Phone : +44 (0)116 2523548, Fax : +44 (0)116 2523555
     
    Nigel Wade, Sep 28, 2007
    #17
  18. ILPTAB

    ILPTAB Guest

    On Sep 28, 7:30 am, Nigel Wade <> wrote:
    > ILPTAB wrote:
    > > Update:
    > > Well I finally got around to trying Nigel's suggestion of calling the
    > > flush() method after the ObjectOutputStream is opened. Unfortunately
    > > this did not resolve the problem.

    >
    > > Can anybody think of a reason why this problem would occur on some
    > > computers and not on others? I know that Roedy suggested that there
    > > may be an issue with the version of a class that has been cached into
    > > the windows browser but the code I posted above was compiled and
    > > published to our web server exactly one time. How could there be a
    > > version conflict with that? That being said I will start adding the
    > > version info to code just in case.

    >
    > > I just find it so darn perplexing that the site works for some people
    > > and not for others.

    >
    > Is there anything in common with the clients which fail? Windows patch level,
    > JRE version, browser etc. I'd go with Roedy's suggestion and use Wireshark to
    > look at the packets on the wire to see what's being sent between the applet and
    > the server.
    >
    >
    >
    > > Could this be a FIREWALL issue?

    >
    > I doubt it, unless it's a badly broken firewall. I don't see how a properly
    > functioning firewall could result in that scenario.
    >
    > --
    > Nigel Wade, System Administrator, Space Plasma Physics Group,
    > University of Leicester, Leicester, LE1 7RH, UK
    > E-mail :
    > Phone : +44 (0)116 2523548, Fax : +44 (0)116 2523555- Hide quoted text -
    >
    > - Show quoted text -


    I have been trying to find that commonality but have not been able to
    put my finger on it yet. Here is something that we did find however"

    After conferring with a technician in the field, we have some
    additional information that we think may help resolve this issue.
    Apparently there is a message line in the Java console that reads
    "Network: Connecting socket://www.ptab.illinois.gov:554 with
    proxy=DIRECT." This is significant because it indicates that the
    Servlet and or applet is forcing a direct connection and is trying to
    circumvent their firewall. The technician tells me that this is why
    the applet is hanging and he believes that it's occurring as a result
    of the way the java application is coded. Unfortunately, I do not
    know how to code this so that it doesn't try to do a direct connect
    instead of going through the proxy. Do you have any idea why this is
    occuring? You can refer to the code I provided above to see how I am
    setting up the socket connection on both sides.

    Thank you.
     
    ILPTAB, Oct 4, 2007
    #18
  19. ILPTAB

    ILPTAB Guest

    On Sep 28, 7:30 am, Nigel Wade <> wrote:
    > ILPTAB wrote:
    > > Update:
    > > Well I finally got around to trying Nigel's suggestion of calling the
    > > flush() method after the ObjectOutputStream is opened. Unfortunately
    > > this did not resolve the problem.

    >
    > > Can anybody think of a reason why this problem would occur on some
    > > computers and not on others? I know that Roedy suggested that there
    > > may be an issue with the version of a class that has been cached into
    > > the windows browser but the code I posted above was compiled and
    > > published to our web server exactly one time. How could there be a
    > > version conflict with that? That being said I will start adding the
    > > version info to code just in case.

    >
    > > I just find it so darn perplexing that the site works for some people
    > > and not for others.

    >
    > Is there anything in common with the clients which fail? Windows patch level,
    > JRE version, browser etc. I'd go with Roedy's suggestion and use Wireshark to
    > look at the packets on the wire to see what's being sent between the applet and
    > the server.
    >
    >
    >
    > > Could this be a FIREWALL issue?

    >
    > I doubt it, unless it's a badly broken firewall. I don't see how a properly
    > functioning firewall could result in that scenario.
    >
    > --
    > Nigel Wade, System Administrator, Space Plasma Physics Group,
    > University of Leicester, Leicester, LE1 7RH, UK
    > E-mail :
    > Phone : +44 (0)116 2523548, Fax : +44 (0)116 2523555- Hide quoted text -
    >
    > - Show quoted text -


    One more thing:
    I have the output from the JAVA console. Maybe this can be of some
    help. Here it is:


    Java Plug-in 1.5.0_05
    Using JRE version 1.5.0_05 Java HotSpot(TM) Client VM
    User home directory = C:\Documents and Settings\sruliso
    network: Loading user-defined proxy configuration ...
    network: Done.
    network: Loading proxy configuration from Internet Explorer ...
    network: Auto config URL: http://webt1resv.ilptab.il.us:8080/array.dll?Get.Routing.Script
    network: Done.
    network: Loading auto proxy configuration ...
    network: Downloading auto proxy file from
    http://webt1resv.ilptab.il.us:8080/array.dll?Get.Routing.Script
    network: Done.
    network: Proxy Configuration: Automatic Proxy Configuration
    URL: http://webt1resv.ilptab.il.us:8080/array.dll?Get.Routing.Script

    basic: Cache is enabled
    basic: Location: C:\Documents and Settings\sruliso\Application Data\Sun
    \Java\Deployment\cache\javapi\v1.0
    basic: Maximum size: unlimited
    basic: Compression level: 0

    ----------------------------------------------------
    c: clear console window
    f: finalize objects on finalization queue
    g: garbage collect
    h: display this help message
    l: dump classloader list
    m: print memory usage
    o: trigger logging
    p: reload proxy configuration
    q: hide console
    r: reload policy configuration
    s: dump system and deployment properties
    t: dump thread list
    v: dump thread stack
    x: clear classloader cache
    0-5: set trace level to <n>
    ----------------------------------------------------

    basic: Registered modality listener
    liveconnect: Invoking JS method: document
    liveconnect: Invoking JS method: URL
    basic: Referencing classloader: sun.plugin.ClassLoaderInfo@199f91c,
    refcount=1
    basic: Registered modality listener
    liveconnect: Invoking JS method: document
    basic: Unregistered modality listener
    basic: Unable to obtain Document object
    basic: Unregistered modality listener
    basic: Registered modality listener
    liveconnect: Invoking JS method: document
    liveconnect: Invoking JS method: URL
    basic: Referencing classloader: sun.plugin.ClassLoaderInfo@199f91c,
    refcount=2
    basic: Added progress listener: sun.plugin.util.GrayBoxPainter@860d49
    basic: Loading applet ...
    basic: Initializing applet ...
    basic: Starting applet ...
    basic: Added progress listener: sun.plugin.util.GrayBoxPainter@910040
    basic: Loading applet ...
    basic: Initializing applet ...
    basic: Starting applet ...
    liveconnect: Invoking JS method: execScript
    liveconnect: Invoking JS method: evalIntermediateValueToReturn
    network: Connecting http://www.ptab.illinois.gov/Applet/PTABLookup.jar
    with proxy=HTTP @ webt1resv.ilptab.il.us/10.44.1.217:8080
    network: Connecting http://www.ptab.illinois.gov/Applet/PTABLookup.jar
    with proxy=HTTP @ webt1resv.ilptab.il.us/10.44.1.217:8080
    basic: Loading http://www.ptab.illinois.gov/Applet/PTABLookup.jar from
    cache
    basic: No certificate info, this is unsigned JAR file.
    www.ptab.illinois.gov
    Development Version
    liveconnect: Invoking JS method: execScript
    liveconnect: Invoking JS method: evalIntermediateValueToReturn
    network: Connecting socket://www.ptab.illinois.gov:554 with
    proxy=DIRECT
    www.ptab.illinois.gov
    Development Version
    network: Connecting socket://www.ptab.illinois.gov:554 with
    proxy=DIRECT
    www.ptab.illinois.gov/163.191.147.10
    www.ptab.illinois.gov/163.191.147.10
    Checkpoint 1 @ Server IO Method.
    Checkpoint 2 @ Server IO Method.
     
    ILPTAB, Oct 4, 2007
    #19
  20. ILPTAB

    ILPTAB Guest

    On Sep 28, 7:30 am, Nigel Wade <> wrote:
    > ILPTAB wrote:
    > > Update:
    > > Well I finally got around to trying Nigel's suggestion of calling the
    > > flush() method after the ObjectOutputStream is opened.  Unfortunately
    > > this did not resolve the problem.

    >
    > > Can anybody think of a reason why this problem would occur on some
    > > computers and not on others?  I know that Roedy suggested that there
    > > may be an issue with the version of a class that has been cached into
    > > the windows browser but the code I posted above was compiled and
    > > published to our web server exactly one time.  How could there be a
    > > version conflict with that?  That being said I will start adding the
    > > version info to code just in case.

    >
    > > I just find it so darn perplexing that the site works for some people
    > > and not for others.

    >
    > Is there anything in common with the clients which fail? Windows patch level,
    > JRE version, browser etc. I'd go with Roedy's suggestion and use Wireshark to
    > look at the packets on the wire to see what's being sent between the applet and
    > the server.
    >
    >
    >
    > > Could this be a FIREWALL issue?

    >
    > I doubt it, unless it's a badly broken firewall. I don't see how a properly
    > functioning firewall could result in that scenario.
    >
    > --
    > Nigel Wade, System Administrator, Space Plasma Physics Group,
    >             University of Leicester, Leicester, LE1 7RH, UK
    > E-mail :    
    > Phone :     +44 (0)116 2523548, Fax : +44 (0)116 2523555- Hide quoted text -
    >
    > - Show quoted text -


    One more piece of info and then I promiss I'll stop. Here is a copy
    the routing script that my web browser calls: I don't pretend to
    understand it but I couldn't help but notice that it has the word
    DIRECT in it all over the place.

    //Copyright (c) 1997 Microsoft Corporation
    BackupRoute="DIRECT";
    UseDirectForLocal=true;
    function MakeIPs(){
    this[0]="10.0.0.0";
    this[1]="255.0.0.0";
    }
    DirectIPs=new MakeIPs();
    cDirectIPs=2;
    function MakeNames(){
    this[0]="*.ilptab.il.us";
    }
    DirectNames=new MakeNames();
    cDirectNames=1;
    cNodes=1;
    function MakeProxies(){
    this[0]=new Node("webT1Resv.ilptab.il.us:8080",0,1.000000);
    }
    Proxies = new MakeProxies();
    function Node(name, hash, load){
    this.name = name;
    this.hash = hash;
    this.load = load;
    this.score = 0;
    return this;
    }
    function FindProxyForURL(url, host){
    var urlhash, ibest, bestscore, list, i, j;
    if (UseDirectForLocal && isPlainHostName(host))
    return "DIRECT";
    if (cDirectNames > 0)
    for (i = 0; i < cDirectNames; i++)
    if (shExpMatch(host, DirectNames))
    return "DIRECT";
    if (cDirectIPs > 0)
    for (i = 0; i < cDirectIPs; i += 2)
    if (isInNet(host, DirectIPs, DirectIPs[i+1]))
    return "DIRECT";
    urlhash = HashString(url);
    for (i = 0; i < cNodes; i++)
    Proxies.score = Proxies.load * Scramble(MakeInt(urlhash ^
    Proxies.hash));
    list = "";
    for (j = 0; j < cNodes; j++) {
    for (bestscore = -1, i = 0; i < cNodes; i++) {
    if (Proxies.score > bestscore) {
    bestscore = Proxies.score;
    ibest = i;
    }
    }
    Proxies[ibest].score = -1;
    list = list + "PROXY " + Proxies[ibest].name + "; ";
    }
    list = list + BackupRoute;
    return list;
    }
    function HashString(url){
    var h = 0;
    var slashes = 0;
    for (var i = 0; i < url.length; i++) {
    var c = url.charAt(i);
    if (c == '/')
    slashes++;
    if (slashes < 3)
    c = c.toLowerCase();
    h += (((h & 0x1fff) << 19) | ((h >> 13) & 0x7ffff)) +
    CharToAscii(c);
    h = MakeInt(h);
    }
    return h;
    }
    function Scramble(h){
    h += ((h & 0xffff) * 0x1965) + ((((h >> 16) & 0xffff) * 0x1965) <<
    16) + (((h & 0xffff) * 0x6253) << 16);
    h = MakeInt(h);
    h += (((h & 0x7ff) << 21) | ((h >> 11) & 0x1fffff));
    return MakeInt(h);
    }
    var Chars =" !\"#$%&\'()*+,-./0123456789:;<=>?
    @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~
    €Â???????????ÂŽÂÂ????????????ž? ¡¢£¤¥¦§¨©ª«¬­®¯°±²³
    ´µ¶·¸¹º»¼½¾¿ÀÃÂÃÄÅÆÇÈÉÊËÌÃÃŽÃÃÑÒÓÔÕÖ×ØÙÚÛÜÃÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþ
    ";
    function CharToAscii(c){
    return Chars.indexOf(c) + 32;
    }
    function MakeInt(x){
    if (x < 0) {
    return x + 4294967296;
    } else if (x >= 4294967296) {
    return x - 4294967296;
    }
    return x;
    }
     
    ILPTAB, Oct 4, 2007
    #20
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