Process monitor / dispatcher in VB6 - vb6

Question

I need to write a little application in VB6 to run instances of another VB6 application and keep an eye on the running processes, but I don't have any idea how to get process information in VB6. I can see some of what I need with the tasklist utility but I don't really know how create processes (specifying the process or application name if possible) and fetching information about processes from the operating system.
This application is to run on a Windows XP machine.
Does anyone know of a get-you-started tutorial or helpful web page for this sort of thing?

Answer 1

There are numerous Windows API functions you can use to do this. I'd start with looking at EnumProcesses (VB6 example and declaration here) which can be used to gather information about all running processes. You can also use OpenProcess
to start interrogating Windows about a particular process (another VB6 example).
There is also a fairly nice example on MSDN.
And of course, there is CreateProcess (AllApi link) or ShellExecute (AllApi) for spawning processes - the former gives you more control over the creation of the process, while the latter is a much simpler call.
There was another question posted about this a while back with some example code.
Another possible approach would be to use WMI (some useful snippets to adapt).
Finally, here are some tutorials that show you how to do it (I'd recommend trying it yourself first though :):
Getting Process Information using PSAPI
Another EnumProcesses/OpenProcess implementation
WMI-based demonstration
Here are some related questions although you probably already saw them when you searched this site before posting:
Monitoring processes to see if they've crashed in vb6
How can I execute a .bat file but wait until its done running before moving on?
How To Enumerate Processes From VB 6 on Win 2003?

Answer 2

Since you say the other application is ** also VB6**, it would be easier to make the other application into an ActiveX exe. Then you can get references to objects in the other application direct from your first application. COM solves it all for you.
Here's Microsoft's tutorial on the subject - you can download the code too.
Or here's another answer where I've written about this

Answer 3

You don't need to go spelunking for processes just to get a handle to child processes that you spawn. The VB6 Shell() function returns a Process ID you can use to call OpenProcess with. CreateProcess gives you the handle directly.
Ok, here is a super-stripped-down example of a program in VB6 to spawn and monitor programs. The example is coded to start and repeatedly restart 3 copies of the command shell (trivial sample child program). It is also written to kill any running children when it is terminated, and there are better alternatives to use in most cases. See A Safer Alternative to TerminateProcess().
This demo also reports back the exit code of each process that quits. You could enter exit 1234 or somesuch to see this in action.
To create the demo open a new VB6 Project with a Form. Add a multiline TextBox Text1 and a Timer Timer1 (which is used to poll the children for completion). Paste this code into the Form:
Option Explicit
Private Const SYNCHRONIZE = &H100000
Private Const PROCESS_QUERY_INFORMATION = &H400&
Private Const PROCESS_TERMINATE = &H1&
Private Const WAIT_OBJECT_0 = 0
Private Const INVALID_HANDLE = -1
Private Const DEAD_HANDLE = -2
Private Declare Function CloseHandle Lib "kernel32" ( _
ByVal hObject As Long) As Long
Private Declare Function GetExitCodeProcess Lib "kernel32" ( _
ByVal hProcess As Long, _
ByRef lpExitCode 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 TerminateProcess Lib "kernel32" ( _
ByVal hProcess As Long, _
ByVal uExitCode As Long) As Long
Private Declare Function WaitForSingleObject Lib "kernel32" ( _
ByVal hHandle As Long, _
ByVal dwMilliseconds As Long) As Long
Private Tasks() As String
Private Handles() As Long
Private Sub Form_Load()
Dim I As Integer
'We'll run 3 copies of the command shell as an example.
ReDim Tasks(2)
ReDim Handles(2)
For I = 0 To 2
Tasks(I) = Environ$("COMSPEC") & " /k ""#ECHO I am #" & CStr(I) & """"
Handles(I) = INVALID_HANDLE
Next
Timer1.Interval = 100
Timer1.Enabled = True
End Sub
Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
Dim I As Integer
Timer1.Enabled = False
DoEvents
For I = 0 To UBound(Tasks)
If Handles(I) <> INVALID_HANDLE And Handles(I) <> DEAD_HANDLE Then
TerminateProcess Handles(I), 666
CloseHandle Handles(I)
Handles(I) = DEAD_HANDLE
End If
Next
End Sub
Private Sub Timer1_Timer()
Dim I As Integer
Dim ExitCode As Long
Dim Pid As Long
Timer1.Enabled = False
For I = 0 To UBound(Tasks)
If Handles(I) <> INVALID_HANDLE Then
If WaitForSingleObject(Handles(I), 0) = WAIT_OBJECT_0 Then
If GetExitCodeProcess(Handles(I), ExitCode) <> 0 Then
Text1.SelText = "Task " & CStr(I) & " terminated, " _
& "exit code: " & CStr(ExitCode) _
& ", restarting task." _
& vbNewLine
Else
Text1.SelText = "Task " & CStr(I) & " terminated, " _
& "failed to retrieve exit code, error " _
& CStr(Err.LastDllError) _
& ", restarting task." _
& vbNewLine
End If
CloseHandle Handles(I)
Handles(I) = INVALID_HANDLE
End If
End If
If Handles(I) = INVALID_HANDLE Then
Pid = Shell(Tasks(I), vbNormalFocus)
If Pid <> 0 Then
Handles(I) = OpenProcess(SYNCHRONIZE _
Or PROCESS_QUERY_INFORMATION _
Or PROCESS_TERMINATE, 0, Pid)
If Handles(I) <> 0 Then
Text1.SelText = "Task " & CStr(I) & " started." _
& vbNewLine
Else
Text1.SelText = "Task " & CStr(I) _
& ", failed to open child process." _
& vbNewLine
Handles(I) = DEAD_HANDLE
End If
Else
Text1.SelText = "Task " & CStr(I) _
& ", failed to Shell child process." _
& vbNewLine
Handles(I) = DEAD_HANDLE
End If
End If
Next
Timer1.Enabled = True
End Sub
Hopefully this helps answer the question.

Answer 4

something more simple will use sockets.
Launch you app server and on your client implements the communication against your server. With that you will provide intercommunication.
well i say. because i dont be what you try do
Sorry it only apply if your clients are done in house i you have the option of added changes