HOWTO: Call EnumServicesStatus API From Visual Basic

• Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, versions 5.0, 6.0
• Microsoft Visual Basic Standard, Professional, and Enterprise Editions, 32-bit only, for Windows, version 4.0

SUMMARY

This article demonstrates how to call the EnumServicesStatus API on Windows NT 4.0 (SP3) from Visual Basic. The EnumServicesStatus function enumerates services in the specified service control manager database. The name and status of each service is retrieved.

MORE INFORMATION

Step-by-Step Instructions

1. Create a new Standard EXE project in Visual Basic, Project1. Form1 is created by default.



2. Place two command buttons and two list boxes on Form1 and place the following code in Form1's code window:

   
         Private Sub Command1_Click()
            'Getting only the active services
               GetServiceInfo SERVICE_ACTIVE
         End Sub
   
         Private Sub Command2_Click()
            'Getting all services registered
               GetServiceInfo SERVICE_ACTIVE Or SERVICE_INACTIVE
         End Sub
   
         Private Sub Form_Load()
            Command1.Caption = "Active Services"
            Command2.Caption = "All Registered Services"
         End Sub
    




3. Add a standard module (Module1) to Project1 and place the following code in Module1.

   
         '****************** MODULE1 CODE **********************
   
         'UDTs
         '*******************************************************
         Type SERVICE_STATUS
            dwServiceType As Long
            dwCurrentState As Long
            dwControlsAccepted As Long
            dwWin32ExitCode As Long
            dwServiceSpecificExitCode As Long
            dwCheckPoint As Long
            dwWaitHint As Long
         End Type
   
         Type ENUM_SERVICE_STATUS
            lpServiceName As Long
            lpDisplayName As Long
            ServiceStatus As SERVICE_STATUS
         End Type
         '*******************************************************
   
         'Constants
         '*******************************************************
         Public Const ERROR_MORE_DATA = 234
         Public Const SERVICE_ACTIVE = &H1
         Public Const SERVICE_INACTIVE = &H2
         Public Const SC_MANAGER_ENUMERATE_SERVICE = &H4
         Public Const SERVICE_WIN32_OWN_PROCESS As Long = &H10
         Public Const SERVICE_WIN32_SHARE_PROCESS As Long = &H20
         Public Const SERVICE_WIN32 As Long = SERVICE_WIN32_OWN_PROCESS _
                     + SERVICE_WIN32_SHARE_PROCESS
         '*******************************************************
   
         'API declarations
         '*******************************************************
         Public Declare Function OpenSCManager Lib "advapi32.dll" _
               Alias "OpenSCManagerA" _
            (ByVal lpMachineName As String, ByVal lpDatabaseName As String, _
                  ByVal dwDesiredAccess As Long) As Long
   
         Public Declare Function EnumServicesStatus Lib "advapi32.dll" _
               Alias "EnumServicesStatusA" (ByVal hSCManager As Long, _
               ByVal dwServiceType As Long, ByVal dwServiceState As Long, _
               lpServices As Any, ByVal cbBufSize As Long, _
               pcbBytesNeeded As Long, lpServicesReturned As Long, _
               lpResumeHandle As Long) As Long
   
         Public Declare Function CloseServiceHandle Lib "advapi32.dll" _
               (ByVal hSCObject As Long) As Long
   
         Public Declare Function lstrcpy Lib "kernel32.dll" Alias "lstrcpyA" _
               (szDest As String, szcSource As Long) As Long
         '*******************************************************
   
         'Where the real work is done.
         '*******************************************************
         Public Sub GetServiceInfo(lngServiceType As Long)
            Dim hSCM As Long
            Dim lpEnumServiceStatus() As ENUM_SERVICE_STATUS
            Dim lngServiceStatusInfoBuffer As Long
            Dim strServiceName As String * 250
            Dim lngBytesNeeded As Long
            Dim lngServicesReturned As Long
            Dim hNextUnreadEntry As Long
            Dim lngStructsNeeded As Long
            Dim lngResult As Long
            Dim i As Long
   
            'Open connection to Service Control Manager.
            hSCM = OpenSCManager(vbNullString, vbNullString, _
                                 SC_MANAGER_ENUMERATE_SERVICE)
   
            If hSCM = 0 Then
               MsgBox "OpenSCManager failed. LastDllError = " _
               & CStr(Err.LastDllError)
               Exit Sub
            End If
   
            'Get buffer size (bytes) without passing a buffer
            'and make sure starts at 0th entry.
            hNextUnreadEntry = 0
            lngResult = EnumServicesStatus(hSCM, _
                                           SERVICE_WIN32, _
                                           lngServiceType, _
                                           ByVal &H0, _
                                           &H0, _
                                           lngBytesNeeded, _
                                           lngServicesReturned, _
                                           hNextUnreadEntry)
   
            'We should receive MORE_DATA error.
            If Not Err.LastDllError = ERROR_MORE_DATA Then
               MsgBox "LastDLLError = " & CStr(Err.LastDllError)
               Exit Sub
            End If
   
            'Calculate the number of structures needed.
            lngStructsNeeded = _
            lngBytesNeeded / Len(lpEnumServiceStatus(0)) + 1
   
            'Redimension the array according to our calculation.
            ReDim lpEnumServiceStatus(lngStructsNeeded - 1)
   
            'Get buffer size in bytes.
            lngServiceStatusInfoBuffer = _
               lngStructsNeeded * Len(lpEnumServiceStatus(0))
   
            'Get services information starting entry 0.
            hNextUnreadEntry = 0
            lngResult = EnumServicesStatus(hSCM, _
                                          SERVICE_WIN32, _
                                          lngServiceType, _
                                          lpEnumServiceStatus(0), _
                                          lngServiceStatusInfoBuffer, _
                                          lngBytesNeeded, _
                                          lngServicesReturned, _
                                          hNextUnreadEntry)
   
            If lngResult = 0 Then
               MsgBox "EnumServicesStatus failed. LastDllError = " _
                  & CStr(Err.LastDllError)
               Exit Sub
            End If
   
   
            'Get the strings and display them.
            With Form1
               .List1.Clear
               .List1.AddItem "Display Names"
               .List2.Clear
               .List2.AddItem "Service Names"
               For i = 0 To lngServicesReturned - 1
                  lngResult = lstrcpy(ByVal strServiceName, _
                     ByVal lpEnumServiceStatus(i).lpDisplayName)
                  .List1.AddItem strServiceName
                  lngResult = lstrcpy(ByVal strServiceName, _
                     ByVal lpEnumServiceStatus(i).lpServiceName)
                  .List2.AddItem strServiceName
               Next
            End With
   
            'Clean up.
            CloseServiceHandle (hSCM)
   
         End Sub
         '******************* END OF MODULE1 **************************
    




4. Run the project.

REFERENCES

Win32 System Services by Marshall Brain

Additional query words: NT Service EnumServicesStatus kbdss kbDSupport kbVBp600 kbNT400sp3 kbVBp
kbVBp400 kbVBp500

Keywords : kbGrpVB
Version :
Platform : WINDOWS
Issue type : kbhowto