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DHCP API

Posted on 2003-10-30
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Last Modified: 2011-09-20
I'm trying to do some DHCP enumerations in VB6.  I'm trying to do a DhcpEnumSubnets call as per MSDN:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dhcp/dhcp/dhcpenumsubnets.asp

I'm apparently having problems porting this over to VB.  Currently with the code below I get bad DLL calling convention.
Any ideas where I'm going wrong?


Here's my code:

Public Const NERR_Success = 0&
Public Const NERR_Access_Denied = 5&
Public Const NERR_MoreData = 234&

Public Declare Sub CopyMem Lib "kernel32" Alias "RtlMoveMemory" _
        (pTo As Any, _
         uFrom As Any, _
         ByVal lSize As Long)
     
'DWORD DHCP_API_FUNCTION DhcpEnumSubnets(
'  DHCP_CONST WCHAR* ServerIpAddress,
'  DHCP_RESUME_HANDLE* ResumeHandle,
'  DWORD PreferredMaximum,
'  LPDHCP_IP_ARRAY* EnumInfo,
'  DWORD* ElementsRead,
'  DWORD* ElementsTotal
');

Declare Function DhcpEnumSubnets Lib "dhcpsapi" _
      (ServerIP As Any, lpResumeHandle As Long, _
      ByVal prefmaxlen As Long, Enuminfo As Long, _
      EntriesRead As Long, TotalEntries As Long)

'typedef struct _DHCP_IP_ARRAY { _
'DWORD NumElements; _
'LPDHCP_IP_ADDRESS Elements;
'} DHCP_IP_ARRAY, *LPDHCP_IP_ARRAY;

'typedef DWORD DHCP_IP_ADDRESS, *PDHCP_IP_ADDRESS, *LPDHCP_IP_ADDRESS;

Type DHCP_IP_ARRAY
   NumElements As Long
   IPaddress As Long
End Type

Public Function DHCPEnum(Server As String)
   Dim yServer() As Byte, lRetCode As Long
   Dim nRead As Long, nTotal As Long
   Dim nret As Long, nResume As Long
   Dim prefmaxlen As Long
   Dim i As Long, x As Long
   Dim lDHCPInfo As Long
   Dim lDHCPInfoPtr As Long
   Dim DHCPInfo As DHCP_IP_ARRAY
     
   yServer = MakeServerName(ByVal Server)
   prefmaxlen = 65536
   nResume = 0

   nret = NERR_MoreData
   Do While (nret = NERR_MoreData)

      nret = DhcpEnumSubnets(yServer(0), nResume, prefmaxlen, _
                      lDHCPInfo, nRead, nTotal)

      If (nret <> NERR_Success And _
       nret <> NERR_MoreData) Then
         'NetError nret
         Debug.Print "Error:" & nret
       
         Exit Do
      End If

      lDHCPInfoPtr = lDHCPInfo
   
      Do While x <= nRead
         CopyMem DHCPInfo, ByVal lDHCPInfoPtr, Len(DHCPInfo)
         Debug.Print DHCPInfo.NumElements
         Debug.Print DHCPInfo.IPaddress
       
         lDHCPInfoPtr = lDHCPInfoPtr + Len(DHCPInfo)
      Loop
   Loop
   
End Function


Public Function MakeServerName(ByVal ServerName As String)
    Dim yServer() As Byte
       
    If ServerName <> "" Then
        If InStr(1, ServerName, "\\") = 0 Then
            ServerName = "\\" & ServerName
        End If
    End If
   
    yServer = ServerName & vbNullChar
    MakeServerName = yServer

End Function
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Question by:Pber
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4 Comments
 
LVL 16

Expert Comment

by:Richie_Simonetti
ID: 9651301
listening...
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LVL 26

Author Comment

by:Pber
ID: 9681729
Do you know what I'm doing wrong converting the API for VB?
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LVL 16

Accepted Solution

by:
Richie_Simonetti earned 125 total points
ID: 9681927
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