I have been struggling with this problem for almost a week now. I need a vb6 application which is running as a service to open a file. I don't need to do anything with the file, I just need it to open. I have tried using ShellExecute and ShellExecuteEx as well as using CreateProcess to attempt to launch the file from the command line. When none of these implementations worked, I tried instead launching another application (using CreateProcess) with the sole task of opening the file and then closing itself.
These solutions all work when the application is run normally, but Not when it is run as a service. It is extremely important that the application be able to open the file while running as a service, either directly or indirectly, it just needs to be able to trigger it.
I understand that Windows has locked down the ability of services to interact with the desktop since Windows Vista, but I'm sure there must be a way to trigger a file open command from a service. The app I've developed is able to run pg_dump.exe (a backup executable for postgres databases) from the command line with CreateProcess to backup database files, while running as a service. That is why I though launching an exe from the service to indirectly open the file might work. However, for some reason the application runs pg_dump.exe fine but will not run the executable I created. I'm wondering if the exe I created is expecting to have some sort of presence on the desktop and that is why the service doesn't want to start it. I changed the properties of the main form in the secondary exe so that the form would not be visible and wouldn't show up on the taskbar, but something tells me that's not enough.
Here is my CreateProcess code (I didn't write most of this so please excuse my ignorance):
Private Declare Function WaitForSingleObject Lib "KERNEL32" (ByVal _
hHandle As Long, ByVal dwMilliseconds As Long) As Long
Private Declare Function CloseHandle Lib "KERNEL32" _
(ByVal hObject As Long) As Long
Private Declare Function GetExitCodeProcess Lib "KERNEL32" _
(ByVal hProcess As Long, lpExitCode As Long) As Long
'create a new win process.
Private Declare Function CreateProcessA Lib "KERNEL32" (ByVal _
lpApplicationName As String, ByVal lpCommandLine As String, ByVal _
lpProcessAttributes As Long, ByVal lpThreadAttributes As Long, _
ByVal bInheritHandles As Long, ByVal dwCreationFlags As Long, _
ByVal lpEnvironment As Long, ByVal lpCurrentDirectory As String, _
lpStartupInfo As STARTUPINFO, lpProcessInformation As _
PROCESS_INFORMATION) As Long
'used by CreateProcess
Private Type STARTUPINFO
cb As Long
lpReserved As String
lpDesktop As String
lpTitle As String
dwX As Long
dwY As Long
dwXSize As Long
dwYSize As Long
dwXCountChars As Long
dwYCountChars As Long
dwFillAttribute As Long
dwFlags As Long
wShowWindow As Integer
cbReserved2 As Integer
lpReserved2 As Long
hStdInput As Long
hStdOutput As Long
hStdError As Long
End Type
Private Type PROCESS_INFORMATION
hProcess As Long
hThread As Long
dwProcessID As Long
dwThreadID As Long
End Type
Const NORMAL_PRIORITY_CLASS = &H20&
Const INFINITE = -1&
Public Function ExecSynchronousCmd(cmdline As String) As Long
' - Used to force a shelled command to run synchronously (code will
' suspend where this function is called until shelled process
' returns a return value)
' - There is no time out - it will wait forever!!
' - Function returns exit value for shelled process
Dim proc As PROCESS_INFORMATION
Dim start As STARTUPINFO
Dim ret As Long
'Initialize the STARTUPINFO structure:
start.cb = Len(start)
'Start the shelled application:
ret = CreateProcessA(vbNullString, cmdline$, 0&, 0&, 1&, _
NORMAL_PRIORITY_CLASS, 0&, vbNullString, start, proc)
'Wait for the shelled application to finish:
ret = WaitForSingleObject(proc.hProcess, INFINITE)
Call GetExitCodeProcess(proc.hProcess, ret&)
Call CloseHandle(proc.hThread)
Call CloseHandle(proc.hProcess)
ExecSynchronousCmd = ret
End Function
Here is the implementation for running pg_dump.exe which is SUCCESSFUL at running the exe From the service and creating database backup files:
i = ExecSynchronousCmd(Chr$(34) & "C:\Program Files (x86)\PostgreSQL\9.3\bin\pg_dump.exe" & Chr$(34) & _
" -Ft " & _
" -f " & Chr$(34) & tempName & Chr$(34) & _
" -U " & s1 & _
" -h " & s3 & _
" -p " & s4 & _
" " & sDB(0, x))
Here is a similar implementation which tries to run the secondary exe that will attempt to open the file in question:
i = ExecSynchronousCmd(Chr$(34) & "C:\Program Files (x86)\GranDocsNP\GDNPOpener.exe" & Chr$(34))
The above code does not work when the app is run as a service. Why is pg_dump.exe successful in running but my own GDNPOpener.exe is not?
As I stated above, I also tried using ShellExecute and ShellExecuteEx to open the file directly from the service, which didn't work. (I am using ShellExecuteEx within the secondary exe (GDNPOpener.exe) to open the file)
If anyone knows how to fix my exe so that my service will run it, I would greatly appreciate the help! If anyone knows any alternative ways to open a file from a service, that would be appreciated as well, thanks!
