VB6, Service - Best Practices

VBClassicGuy: Thanks, I did see other people talk about sleep not being that great.  But I'm not sure I understand your code though.  Well I mean I understand the code as its written but don't know how you mean to use it.  I'm assuming there is more to it that i'm not getting

Brook1966: Thanks, Good idea on the logging.

So I'm guess i'm still looking for how to tell when my applicaiton is ending.  So for example I guess I was picturing someone shutting down their machine and me having some sort of event to change my variable of EndNow to True so that it would fall threw the loop and do the final sub of 'DoFinalTasks' so that I can wite one last time to a database.  You know just like I could do in a forms Form_Unload() sub. (But again I don't have any forms all code is just in 1 modual)

Thanks!

you could put that code in the Form_Unload event

public sub Form_Unload()
  update database or write to log here

end sub

but  you are not using a form....

My code snippet just "pauses" (or "sleeps", if you prefer) your program for the specified number of seconds. In the case of the example, 10 seconds. The advantage over the Sleep command is that it doesn't hog the CPU cycles. The DoEvents statement lets the PC perform other duties like updating the screen, responding to other program's needs, etc. In other words, it won't "freeze" your PC for 10 seconds like Sleep will.

By the way, if someone shuts down your PC, you will need an API call on a fast timer to detect the "kill application" message sent to your program, so you can do your EndNow thing. But shutdowns can still sneak by you if timed just right. And, if someone cuts off the power, unplugs the PC, or there is a power outage, you're SOL. And we haven't even talked about untrapped errors causing the program to terminate.

I have an "Event Log" in my programs that keeps track of everytime a user starts the program, and everytime they exit it. I don't even bother with trying to catch shutdowns, blackouts, and errors. I just know in the log that if I see to "IN"'s in a row without an "OUT" between them, the program terminated abnormally.

VBClassicGuy: got the timer thing finally, my problem was I didn't realize that "timer" was actually a built in function of VB6.  Wrote a small sub to pass number of seconds too pause for and the timer code you supplied works great!  Good info!

As for the part on knowing when the exe is ending... hmmm wonder if maybe I should just make this a standard exe with a hidden form and make it run on startup of the PC instead of making it a service.  My thought on making it a service was I didn't want our users to see it and be able to end task on it.

The point of my app is: we have some accounting software here they need to know who is actively connected to it because sometimes they need everyone out so they can do certain tasks in it which require every out except the person doing the task.  So usually they send out email after email telling everyone to get out but inevitably someone left it running while they stepped out.  So I wrote this small app to check if the accounting apps process is running on a machine and write back to a database the user name, ip, workstation name and if its running or not back to a database.  Then I have a simple web page management can look at to see who is running it.  Everything works fine in development Im at the point now of putting it on everyones machines and was trying to come up with the "best way" to implement it on users machines.  Just making it an exe that runs on startup with a hidden form seemed not stupid proof enough for some of our users since they can see it in the task manger and end task on.  :)

But maybe thats the best I can do?  Any suggestions now fully knowing the scenario? (I'll answer back tomorrow Im just heading out)  Thanks again.

I have some programs that must stay running all the time, or data is lost. For these apps, I remove the "X" in the main form's upper right-hand corner, remove "Close" and "Maximize" from the system menu so they can only Minimize and Restore, and put in an "Easter egg" to get the Exit button to enable. Only high-level managers know of this "back door" and can exit the program. Most of my customers are too PC illiterate to know how to use Task Manager.

This back door is usually something like "hold down the Shift key and right-click on a certain control (maybe the PictureBox containing our logo), then enter the password". On a really secure program, this password changes daily (there is code in the program to generate the password-of-the-day, and managers are given an applet that generates this password).

I figure that's the best i can do. No program is 100% safe as long as a 16-year-old hacker/gamer is available LOL.

Oh by the way, if your users can kill an app by using Task Manager, they can also stop the service from the Processes tab. Not much you can do if someone really, really wants to stop your program/service.

<<< My thought on making it a service was I didn't want our users to see it and be able to end task on it. >>>

Add code to a form, Compile to exe run it and try terminate the process.

Let this be your warning :)

Option Explicit
 
Private Const SE_PRIVILEGE_ENABLED As Long = &H2&
Private Const TOKEN_ADJUST_PRIVILEGES As Long = &H20&
Private Const TOKEN_QUERY As Long = &H8&
 
Private Type LUID
LowPart As Long
HighPart As Long
End Type
 
Private Type TOKEN_PRIVILEGES
PrivilegeCount As Long
LuidUDT As LUID
Attributes As Long
End Type
 
Private Declare Function OpenProcessToken Lib "advapi32" (ByVal ProcessHandle As Long, ByVal DesiredAccess As Long, ByRef TokenHandle As Long) As Long
Private Declare Function LookupPrivilegeValueW Lib "advapi32" (ByVal lpSystemName As Long, ByVal lpName As Long, ByRef lpLuid As LUID) As Long
Private Declare Function AdjustTokenPrivileges Lib "advapi32" (ByVal TokenHandle As Long, ByVal DisableAllPrivileges As Long, ByRef NewState As TOKEN_PRIVILEGES, ByVal BufferLength As Long, ByRef PreviousState As Any, ByRef ReturnLength As Any) As Long
Private Declare Function GetCurrentProcess Lib "kernel32" () As Long
Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
 
Private Declare Function LoadLibraryA Lib "kernel32.dll" (ByVal lpLibFileName As String) As Long
Private Declare Function GetProcAddress Lib "kernel32.dll" (ByVal hModule As Long, ByVal lpProcName As String) As Long
Private Declare Function CallWindowProcA Lib "user32.dll" (ByVal lpPrevWndFunc As Long, ByVal hWnd As Long, ByVal uMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Private Declare Function FreeLibrary Lib "kernel32.dll" (ByVal hLibModule As Long) As Long
 
Private Sub EnablePrivilege(ByVal szPrivilegeName As String)
 
    Dim hToken          As Long
    Dim TokenPriv       As TOKEN_PRIVILEGES
    
    ' Query the token
    Call OpenProcessToken(GetCurrentProcess, _
        TOKEN_ADJUST_PRIVILEGES Or _
        TOKEN_QUERY, hToken)
        
    Call LookupPrivilegeValueW(0, _
        StrPtr(szPrivilegeName), _
        TokenPriv.LuidUDT)
        
    ' Enable
    TokenPriv.PrivilegeCount = 1
    TokenPriv.Attributes = SE_PRIVILEGE_ENABLED
    
    ' Attempts to adjust the privilege.
    Call AdjustTokenPrivileges(hToken, 0, TokenPriv, 0, ByVal 0&, ByVal 0&)
 
    CloseHandle hToken
    
End Sub
 
Public Sub ProtectProcess()
    
    Dim hMod        As Long
    Dim Addr        As Long
    
    Call EnablePrivilege("SeDebugPrivilege")
    
    hMod = LoadLibraryA("ntdll.dll")
    
    If hMod <> 0 Then
       Addr = GetProcAddress(hMod, "RtlSetProcessIsCritical")
       Addr = CallWindowProcA(Addr, 1, 0, 0, 0)
    End If
 
End Sub
 
Private Sub Form_Load()
  Call ProtectProcess
End Sub

                                              

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Very impressive, egl1044. That's one of those pieces of code one wants to squirrel away in case you need it down the road. Good job!

lol :)

Thanks egl1044.  I tried the code and got a Blue Screen of Death so a bit nervous about trying it again.  Basically I added a new modual, plopped in the code.  Ran the project.  Stopped the Project.  Compiled an EXE.  Ran the exe.  Didn't see it listed in processes.  Then since the form is hidden on it just for testing after 60 seconds i made it pop up a window and ask if i wated to exit.  I said yes and in code is just calls "unload me".  Thats then i got the BSoD.

BSoD message:
A process or thread crucial to system opration has unexpectedly exited or been terminated
...the usual other info...
STOP 0x0000000F4 (0x00000003, 0x89AOD670, 0x89AOD7E4, 0x805D297C)

Any ideas on why this might have happened?

That is the intended behavior of the code. Because the process bit flag was changed to (critical) windows thinks it's a critical process that needs to be running for the operating system to work.
The code was just some geek humor to show that it's not a very good idea to stop a user from ending a process. :)

egl1044: I'll take that with a grain of salt since you gave me about what I asked for - although I really just wanted to hide the process from the task manager not BSoD a machine if the process was stopped.  But your warning of: "Let this be your warning :)" didn't make me think hey this will BSoD my computer losing any changes to any documents I had open.  Might be a tiny bit more specific next time for those of us who just code as part of their jobs and aren't code geeks.

VBClassicGuy: Thanks for all the help and suggestions!  I think I'll just go the easy route and make this a normal exe with a hidden form that starts on startup.  I'll let management worry about people not running the software after I'm done putting it on peoples machines.

End result wasn't what I had origianlly asked for but got some good info!

<< hide the process from the task manager >>

Here is a small trick if your worried about task manager :)

The only way to actually prevent a process is what I showed, or hooking TerminateProcess.

Dim hFile As Long
 
Private Sub Command1_Click()
Close #hFile
End Sub
 
Private Sub Form_Load()
hFile = FreeFile
Open "c:\windows\system32\taskmgr.exe" For Binary Lock Read As #hFile
End Sub

                                              

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Yeah, I run into similar situations with my customers. They want the program to do impossible (or VERY difficult) things to make up for their employee's "curiosity" or "playfulness". Some times I feel like telling them, "Look, at some point the user or management needs to take responsibility for their actions. Just add it to your rules...no guns at work, no drinking on the job or coming in intoxicated, no drugs, and YOU MUST RUN THIS PROGRAM to do your normal job functions. Period."