HOW TO: Access the Registry on a Remote Computer by Using Visual Basic 6.0 and the Windows API

This article explains how to use a Visual Basic application to access the registry on a remote computer in conjunction with the Windows application programming interface (API).

Requirements

You need the following hardware and software to perform the procedures in this article:

• A Microsoft Windows XP, Microsoft Windows 2000, or Microsoft Windows NT 4.0-based computer
• Visual Basic 6.0

NOTE: If the remote registry is on a system that is running Windows NT 4.0, Windows 2000, or Windows XP, you must run the code from an account that has permission to read that registry.

You also need the following skills:

• Visual Basic 6.0 programming experience
• Familiarity with the Windows registry

Create a Demonstration Application

1. Start Visual Basic 6.0, and then create a new project of type Standard EXE.
2. Right-click the form, and then click View Code on the Shortcut menu. Add the following statement at the start of the code:

   Option Explicit
   					

3. Add the following code to declare the constants used to access the registry:

   Private Const HKEY_CLASSES_ROOT = &H80000000
   Private Const HKEY_CURRENT_USER = &H80000001
   Private Const HKEY_LOCAL_MACHINE = &H80000002
   Private Const HKEY_USERS = &H80000003
   
   Private Const KEY_QUERY_VALUE = &H1
   Private Const KEY_SET_VALUE = &H2
   Private Const KEY_ALL_ACCESS = &H3F
   
   Private Const REG_SZ  As Long = 1
   Private Const ERROR_SUCCESS = 0&
   					

4. Add the following code to declare the entry points for the registry functions in the Windows application programming interface (API):

   Private Declare Function RegConnectRegistry Lib "advapi32.dll" _
   Alias "RegConnectRegistryA" _
       (ByVal lpMachineName As String, _
        ByVal hKey As Long, _
        phkResult As Long) As Long
   
   Private Declare Function RegCloseKey Lib "advapi32.dll" _
       (ByVal hKey As Long) As Long
   
   Private Declare Function RegOpenKeyEx Lib "advapi32.dll" _
   Alias "RegOpenKeyExA" _
       (ByVal hKey As Long, _
        ByVal lpSubKey As String, _
        ByVal ulOptions As Long, _
        ByVal samDesired As Long, _
        phkResult As Long) As Long
      
   Private Declare Function RegQueryValueExString Lib "advapi32.dll" _
   Alias "RegQueryValueExA" _
       (ByVal hKey As Long, _
        ByVal lpValueName As String, _
        ByVal lpReserved As Long, _
        lpType As Long, _
        ByVal lpData As String, _
        lpcbData As Long) As Long
   					

5. Add the following global variable declaration:

   Private hRemoteReg As Long
   					

6. Add the following code to handle the Form_Load event. This code calls the RegConnectRegistry function to connect to the remote registry. Replace the \\RemoteMachineName parameter with the name of the computer whose registry you want to access:

   Private Sub Form_Load()
       Dim lRet As Long
       
       'Connect to the remote registry 
       lRet = RegConnectRegistry("\\RemoteMachineName", _
                                 HKEY_LOCAL_MACHINE, _
                                 hRemoteReg)
       
       If (lRet = ERROR_SUCCESS) Then
           MsgBox "Successfully connected to remote registry"
       Else
           MsgBox "Error:" & Err.LastDllError
           Unload Me
           Exit Sub
       End If
   End Sub
   					

7. Add the following code to handle the Form_Unload event:

   Private Sub Form_Unload(Cancel As Integer)
       Dim lRet As Long
       If hRemoteReg <> 0 Then
           lRet = RegCloseKey(hRemoteReg)
       End If
   End Sub
   					

8. In the Form Designer, add a Command control to the form. The control has the default name of Command1.
9. Double-click Command1 to create a click handler for the command button. Add the following code to the click handler function:

   Private Sub Command1_Click()
       Dim lRetVal As Long
       Dim hKey As Long
       Dim sValue As String
       
       lRetVal = RegOpenKeyEx(hRemoteReg, _
           "HARDWARE\DESCRIPTION\System", 0, KEY_QUERY_VALUE, hKey)
       If lRetVal <> ERROR_SUCCESS Then
           MsgBox "Cannot open key"
       Else
           sValue = String(255, " ")
           lRetVal = RegQueryValueExString(hKey, _
               "SystemBIOSVersion", 0&, REG_SZ, sValue, 255)
           If lRetVal <> ERROR_SUCCESS Then
               MsgBox "Cannot query value"
           Else
               MsgBox sValue
           End If
           lRetVal = RegCloseKey(hKey)
           If lRetVal <> ERROR_SUCCESS Then
               MsgBox "Cannot close key"
           End If
       End If
   End Sub
   					

Verification

1. Press F5 to build and run the application.
2. A message box appears, indicating that the registry on the remote computer has been contacted. Click OK.
   
   The main form of the application appears.
3. Click Command1. The value stored in the following location in the remote registry is displayed:
   HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\SystemBIOSVersion
4. To verify this registry value, run regedit.exe on the remote computer. In Registry Editor, click Find on the Edit menu. Type SystemBIOSVersion, and then click Find Next. After a short pause, Registry Editor displays the value for this key; verify that this is the same value displayed in your Visual Basic application.

For additional information, click the article number below to view the article in the Microsoft Knowledge Base: