DOCUMENT:Q231844  20-JUL-2001  [vbwin]
TITLE   :HOWTO: Detect If an Application Has Stopped Responding
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER::4.01,4.01 SP1,4.01 SP2,5,5.0,5.5,6.0
OPER/SYS:
KEYWORDS:kbie401 kbVBp500 kbVBp600 kbie401sp1 kbie401sp2 kbGrpDSInet kbie500 kbie550

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The information in this article applies to:

 - Microsoft Visual Basic Learning Edition for Windows, versions 5.0, 6.0 
 - Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0 
 - Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
 - Microsoft Internet Explorer (Programming) versions 4.01, 4.01 SP1, 4.01 SP2, 5, 5.5 
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SUMMARY
=======

In many situations you might like to detect if an application is blocked. For
example while automating Internet Explorer, you'd like to know if Internet
Explorer has stopped responding.

This article describes how to detect if an automated instance of Internet
Explorer is hung or not. Although the code is written for Internet Explorer and
Visual Basic, the idea can be used for other applications as well.

The code uses the Win32 API SendMessageTimout function to determine if the target
application is responding and the API call TerminateProcess to kill the hung
instance of Internet Explorer.

MORE INFORMATION
================

There is no clear definition of an application hanging. Typically the
application is "busy" with some processing. However from a user's perspective,
the application has stopped responding.

The idea is to periodically detect if the application is still responding in a
timer and depending on application logic, the target application can be killed
or other necessary action can be taken.
The following steps demonstrate this. The code assumes that Internet Explorer is
installed on the target machine.

1. Start a new Standard EXE project in Visual Basic.

2. Form1 is created by default. Place three command buttons on the form and name
   them cmdCheck, cmdLaunch, and cmdKill. Change their Caption property to
   Check, Launch, and Kill, respectively.

3. Add the following code to Form1:

   Option Explicit

   'API Constants
   Const SMTO_BLOCK = &H1
   Const SMTO_ABORTIFHUNG = &H2
   Const WM_NULL = &H0
   Const WM_CLOSE = &H10
   Const PROCESS_ALL_ACCESS = &H1F0FFF
   'API functions
   Private Declare Function GetWindowThreadProcessId Lib "user32" (ByVal hwnd As Long, _
   lpdwProcessId As Long) As Long

   Private Declare Function OpenProcess Lib "kernel32" (ByVal dwDesiredAccess As Long, _
   ByVal bInheritHandle As Long, ByVal dwProcessId As Long) As Long

   Private Declare Function SendMessageTimeout Lib "user32" Alias "SendMessageTimeoutA" _
   (ByVal hwnd As Long, ByVal msg As Long, ByVal wParam As Long, ByVal lParam As _
   Long, ByVal fuFlags As Long, ByVal uTimeout As Long, lpdwResult As Long) As Long

   Private Declare Function TerminateProcess Lib "kernel32" (ByVal hProcess As Long, _
   ByVal uExitCode As Long) As Long

   Private modObjIE As Object
   Private modlngWndIE As Long

   Private Sub cmdCheck_Click()
       Dim lngResult As Long
       Dim lngReturnValue As Long
       lngReturnValue = SendMessageTimeout(modlngWndIE, WM_NULL, 0&, 
         0&, SMTO_ABORTIFHUNG And SMTO_BLOCK, 1000, lngResult)
       If lngReturnValue Then
           MsgBox "Responding"
       Else
           MsgBox "Not Responding","Block tester"
       End If
   End Sub

   Private Sub cmdLaunch_Click()
       Set modObjIE = Nothing
       Set modObjIE = CreateObject("InternetExplorer.Application")
       modObjIE.Visible = True
       modObjIE.Navigate2 "http://www.microsoft.com"
       modlngWndIE = modObjIE.hwnd
   End Sub

   Private Sub cmdKill_Click()
       Dim lngProcessID As Long
       Dim lngReturnValue As Long
       Dim lngProcess As Long
       lngReturnValue = GetWindowThreadProcessId(modlngWndIE, lngProcessID)
       lngProcess = OpenProcess(PROCESS_ALL_ACCESS, 0&, lngProcessID)
       lngReturnValue = TerminateProcess(lngProcess, 0&)
   End Sub

4. Run this program and click the Launch button.

5. Click the Check button. You should see Responding appear.

Enter your own URL in the navigate2 command if you have one that causes
blocking.

NOTE: None of the automation properties of Internet Explorer will be accessible
once Internet Explorer stops responding, which is the reason for storing hwnd in
a form level variable.


REFERENCES
==========

For additional information, click the article numbers below to view the articles
in the Microsoft Knowledge Base:

   Q129797 HOWTO: Launch a Win32 Application from Visual Basic

   Q178893 HOWTO: Terminate an Application Cleanly in Win32

   Q176391 HOWTO: Programmatically Close a Separate Application


Additional query words: SendMessageTimeout GetWindowThreadProcessId TerminateProcess hangs hung kill terminate IE "Internet Explorer" freezes blocked blocks "stops responding" "not

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Keywords          : kbie401 kbVBp500 kbVBp600 kbie401sp1 kbie401sp2 kbGrpDSInet kbie500 kbie550 
Technology        : kbVBSearch kbIEsearch kbAudDeveloper kbZNotKeyword6 kbSDKIESearch kbZNotKeyword2 kbVB500Search kbVB600Search kbVB500 kbVB600 kbIE500Search kbSDKIE401 kbSDKIE401SP1 kbSDKIE401SP2 kbSDKIE500 kbSDKIE550 kbIE550Search
Version           : :4.01,4.01 SP1,4.01 SP2,5,5.0,5.5,6.0
Issue type        : kbhowto

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Copyright Microsoft Corporation 2001.