How to access structure pointer returned by Windows API

Dear all,

I'm trying to get MAC Address by calling Windows API (GetAdaptersInfo).

Which return all adapters information in a linked list style. Each structure
consist information of

one adapter and there is a pointer 'Next' which is a pointer to next
structure.

I declare this 'Next' pointer as LONG in VBA.

Now I can access the 1st structure only. Can anyone tell me how to use the
'Next' pointer to access other structures?

Thanks for help.

 

This also isn't specifically what you asked for, but it might help.
There are links to other methods of obtaining the mac address as well.

http://vbnet.mvps.org/code/network/macaddressremote.htm

Hope that helps,
Danny Polkinhorn
WATG
Honolulu

 

Dear All,

Thanks for help.

 

Hi Bob,

Thanks for your help. I've tried the attached spreadsheet program. It works
fine if the connection is in active state.

But if the network cable is disconnected the program returns all zeros.
Because of this I need to use the API 'GetAdaptersInfo'.

Which returns all adapters information even the network cable is
disconnected.

Anyway thanks for your comment.

 

Stanley,

Understood, sorry about the spreadsheet, one of those had-n-grab code examples. Try this snippet then for GetAdaptersInfo API specific. I believe this addresses your original question iterating through the structure.

Public Const MAX_HOSTNAME_LEN = 132
Public Const MAX_DOMAIN_NAME_LEN = 132
Public Const MAX_SCOPE_ID_LEN = 260
Public Const MAX_ADAPTER_NAME_LENGTH = 260
Public Const MAX_ADAPTER_ADDRESS_LENGTH = 8
Public Const MAX_ADAPTER_DESCRIPTION_LENGTH = 132
Public Const ERROR_BUFFER_OVERFLOW = 111
Public Const MIB_IF_TYPE_ETHERNET = 1
Public Const MIB_IF_TYPE_TOKENRING = 2
Public Const MIB_IF_TYPE_FDDI = 3
Public Const MIB_IF_TYPE_PPP = 4
Public Const MIB_IF_TYPE_LOOPBACK = 5
Public Const MIB_IF_TYPE_SLIP = 6

Type IP_ADDR_STRING
Next As Long
IpAddress As String * 16
IpMask As String * 16
Context As Long
End Type

Type IP_ADAPTER_INFO
Next As Long
ComboIndex As Long
AdapterName As String * MAX_ADAPTER_NAME_LENGTH
Description As String * MAX_ADAPTER_DESCRIPTION_LENGTH
AddressLength As Long
Address(MAX_ADAPTER_ADDRESS_LENGTH - 1) As Byte
Index As Long
Type As Long
DhcpEnabled As Long
CurrentIpAddress As Long
IpAddressList As IP_ADDR_STRING
GatewayList As IP_ADDR_STRING
DhcpServer As IP_ADDR_STRING
HaveWins As Boolean
PrimaryWinsServer As IP_ADDR_STRING
SecondaryWinsServer As IP_ADDR_STRING
LeaseObtained As Long
LeaseExpires As Long
End Type

Type FIXED_INFO
HostName As String * MAX_HOSTNAME_LEN
DomainName As String * MAX_DOMAIN_NAME_LEN
CurrentDnsServer As Long
DnsServerList As IP_ADDR_STRING
NodeType As Long
ScopeId As String * MAX_SCOPE_ID_LEN
EnableRouting As Long
EnableProxy As Long
EnableDns As Long
End Type

Public Declare Function GetNetworkParams Lib "IPHlpApi" (FixedInfo As Any, pOutBufLen As Long) As Long
Public Declare Function GetAdaptersInfo Lib "IPHlpApi" (IpAdapterInfo As Any, pOutBufLen As Long) As Long
Public Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As Long)
Sub main()
Dim error As Long
Dim FixedInfoSize As Long
Dim AdapterInfoSize As Long
Dim i As Integer
Dim PhysicalAddress As String
Dim NewTime As Date
Dim AdapterInfo As IP_ADAPTER_INFO
Dim Adapt As IP_ADAPTER_INFO
Dim AddrStr As IP_ADDR_STRING
Dim FixedInfo As FIXED_INFO
Dim Buffer As IP_ADDR_STRING
Dim pAddrStr As Long
Dim pAdapt As Long
Dim Buffer2 As IP_ADAPTER_INFO
Dim FixedInfoBuffer() As Byte
Dim AdapterInfoBuffer() As Byte

'Get the main IP configuration information for this machine using a FIXED_INFO structure
FixedInfoSize = 0
error = GetNetworkParams(ByVal 0&, FixedInfoSize)
If error <> 0 Then
If error <> ERROR_BUFFER_OVERFLOW Then
MsgBox "GetNetworkParams sizing failed with error " & error
Exit Sub
End If
End If
ReDim FixedInfoBuffer(FixedInfoSize - 1)

error = GetNetworkParams(FixedInfoBuffer(0), FixedInfoSize)
If error = 0 Then
CopyMemory FixedInfo, FixedInfoBuffer(0), Len(FixedInfo)
MsgBox "Host Name: " & FixedInfo.HostName 'host name
MsgBox "DNS Servers: " & FixedInfo.DnsServerList.IpAddress 'dns server IP
pAddrStr = FixedInfo.DnsServerList.Next
Do While pAddrStr <> 0
CopyMemory Buffer, ByVal pAddrStr, Len(Buffer)
MsgBox "DNS Servers: " & Buffer.IpAddress 'dns server IP
pAddrStr = Buffer.Next
Loop

Select Case FixedInfo.NodeType 'node type
Case 1
MsgBox "Node type: Broadcast"
Case 2
MsgBox "Node type: Peer to peer"
Case 4
MsgBox "Node type: Mixed"
Case 8
MsgBox "Node type: Hybrid"
Case Else
MsgBox "Unknown node type"
End Select

MsgBox "NetBIOS Scope ID: " & FixedInfo.ScopeId 'scope ID
'routing
If FixedInfo.EnableRouting Then
MsgBox "IP Routing Enabled "
Else
MsgBox "IP Routing not enabled"
End If
' proxy
If FixedInfo.EnableProxy Then
MsgBox "WINS Proxy Enabled "
Else
MsgBox "WINS Proxy not Enabled "
End If
' netbios
If FixedInfo.EnableDns Then
MsgBox "NetBIOS Resolution Uses DNS "
Else
MsgBox "NetBIOS Resolution Does not use DNS "
End If
Else
MsgBox "GetNetworkParams failed with error " & error
Exit Sub
End If

'Enumerate all of the adapter specific information using the IP_ADAPTER_INFO structure.
'Note: IP_ADAPTER_INFO contains a linked list of adapter entries.

AdapterInfoSize = 0
error = GetAdaptersInfo(ByVal 0&, AdapterInfoSize)
If error <> 0 Then
If error <> ERROR_BUFFER_OVERFLOW Then
MsgBox "GetAdaptersInfo sizing failed with error " & error
Exit Sub
End If
End If
ReDim AdapterInfoBuffer(AdapterInfoSize - 1)

' Get actual adapter information
error = GetAdaptersInfo(AdapterInfoBuffer(0), AdapterInfoSize)
If error <> 0 Then
MsgBox "GetAdaptersInfo failed with error " & error
Exit Sub
End If
CopyMemory AdapterInfo, AdapterInfoBuffer(0), Len(AdapterInfo)
pAdapt = AdapterInfo.Next

Do While pAdapt <> 0
CopyMemory Buffer2, AdapterInfo, Len(Buffer2)
Select Case Buffer2.Type
Case MIB_IF_TYPE_ETHERNET
MsgBox "Ethernet adapter "
Case MIB_IF_TYPE_TOKENRING
MsgBox "Token Ring adapter "
Case MIB_IF_TYPE_FDDI
MsgBox "FDDI adapter "
Case MIB_IF_TYPE_PPP
MsgBox "PPP adapter"
Case MIB_IF_TYPE_LOOPBACK
MsgBox "Loopback adapter "
Case MIB_IF_TYPE_SLIP
MsgBox "Slip adapter "
Case Else
MsgBox "Other adapter "
End Select
MsgBox " AdapterName: " & Buffer2.AdapterName
MsgBox "AdapterDescription: " & Buffer2.Description 'adatpter name

For i = 0 To Buffer2.AddressLength - 1
PhysicalAddress = PhysicalAddress & Hex(Buffer2.Address(i))
If i < Buffer2.AddressLength - 1 Then
PhysicalAddress = PhysicalAddress & "-"
End If

Next
MsgBox "Physical Address: " & PhysicalAddress 'mac address
If Buffer2.DhcpEnabled Then
MsgBox "DHCP Enabled "
Else
MsgBox "DHCP disabled"
End If

pAddrStr = Buffer2.IpAddressList.Next
Do While pAddrStr <> 0
CopyMemory Buffer, Buffer2.IpAddressList, LenB(Buffer)
MsgBox "IP Address: " & Buffer.IpAddress
MsgBox "Subnet Mask: " & Buffer.IpMask
pAddrStr = Buffer.Next
If pAddrStr <> 0 Then
CopyMemory Buffer2.IpAddressList, ByVal pAddrStr, Len(Buffer2.IpAddressList)
End If
Loop
MsgBox "Default Gateway: " & Buffer2.GatewayList.IpAddress
pAddrStr = Buffer2.GatewayList.Next
Do While pAddrStr <> 0
CopyMemory Buffer, Buffer2.GatewayList, Len(Buffer)
MsgBox "IP Address: " & Buffer.IpAddress
pAddrStr = Buffer.Next
If pAddrStr <> 0 Then
CopyMemory Buffer2.GatewayList, ByVal pAddrStr, Len(Buffer2.GatewayList)
End If
Loop

MsgBox "DHCP Server: " & Buffer2.DhcpServer.IpAddress
MsgBox "Primary WINS Server: " & Buffer2.PrimaryWinsServer.IpAddress
MsgBox "Secondary WINS Server: " & Buffer2.SecondaryWinsServer.IpAddress

' Display time
NewTime = CDate(Adapt.LeaseObtained)
MsgBox "Lease Obtained: " & CStr(NewTime)

NewTime = CDate(Adapt.LeaseExpires)
MsgBox "Lease Expires : " & CStr(NewTime)
pAdapt = Buffer2.Next
If pAdapt <> 0 Then
CopyMemory AdapterInfo, ByVal pAdapt, Len(AdapterInfo)
End If

Loop

End Sub


Regards and good luck,

Bob Coward
CADS, Inc

800-366-0946

 

Dear Bob,

Thank you. I've learn so much from you.

Best regards.

Stanley.

 

And a Merry Christmas to you too...Happy holidays all