How To Detect If an Application Has Stopped Responding (231844)

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.