Visual Basic Network Services
Netbios: Determine Local Adapter MAC Addresses through LANA Enumeration
Posted:   Sunday April 18, 2004
Updated:   Monday December 26, 2011
Applies to:   VB4-32, VB5, VB6
Developed with:   VB6, Windows XP
OS restrictions:   None
Author:   VBnet - Randy Birch


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Installed network card or cards, NetBIOS.

Netbios: Determine Local Adapter MAC Address shows how to retrieve the Medium Access Control (MAC) address for the installed network card. A MAC Address is a unique 48-bit number assigned to the network interface card (NIC) by the manufacturer. On systems with multiple NICs the above routine returns only the MAC address of the first NIC (LANA=0). Since machines can easily support multiple NICs, a method to determine the MAC address of each is required and is presented here.

Retrieving a MAC address using this code requires two things - first, each of the adapters must be active (enabled) in Windows - it can not be disabled through the network settings - just being present in the computer is not enough. The second prerequisite is each adapter must be bound to the NetBIOS protocol either implicilty (NetBIOS protocol assigned to the adapter) or as part of a combined protocol (e.g. IPX/SPX/NetBIOS-compatible Transport Protocol).

My system has two network cards, although typically only one is ever used.  The first illustration (number of adapters = 1) shows the result of the code below when only this adapter is enabled. Illustration two shows the result of the same code with both adapters enabled.

 BAS Module Code

 Form Code
To a form add a command button (Command1) and a list box (List1) along with the following code:

Option Explicit
' Copyright 1996-2011 VBnet/Randy Birch, All Rights Reserved.
' Some pages may also contain other copyrights by the author.
' Distribution: You can freely use this code in your own
'               applications, but you may not reproduce 
'               or publish this code on any web site,
'               online service, or distribute as source 
'               on any media without express permission.
Private Const NCBASTAT As Long = &H33
Private Const NCBRESET As Long = &H32
Private Const NCBENUM As Long = &H37    
Private Const NRC_GOODRET As Long = &H0
Private Const MAX_LANA As Long = 254
Private Const NCBNAMSZ As Long = 16
Private Const HEAP_ZERO_MEMORY As Long = &H8

Private Type LANA_ENUM
   length As Byte
   adapter_numbers(0 To MAX_LANA) As Byte 'lanas in range 0 to MAX_LANA inclusive
End Type

   ncb_command As Byte
   ncb_retcode As Byte
   ncb_lsn As Byte
   ncb_num As Byte
   ncb_buffer As Long
   ncb_length As Integer
   ncb_callname As String * NCBNAMSZ
   ncb_name As String * NCBNAMSZ
   ncb_rto As Byte
   ncb_sto As Byte
   ncb_post As Long
   ncb_lana_num As Byte
   ncb_cmd_cplt As Byte
   ncb_reserve(0 To 9) As Byte 'if Win64, make (0 to 17)
   ncb_event As Long
End Type

   adapter_address(0 To 5) As Byte '6 elements
   rev_major As Byte
   reserved0 As Byte
   adapter_type As Byte
   rev_minor As Byte
   duration As Integer
   frmr_recv As Integer
   frmr_xmit As Integer
   iframe_recv_err As Integer
   xmit_aborts As Integer
   xmit_success As Long
   recv_success As Long
   iframe_xmit_err As Integer
   recv_buff_unavail As Integer
   t1_timeouts As Integer
   ti_timeouts As Integer
   Reserved1 As Long
   free_ncbs As Integer
   max_cfg_ncbs As Integer
   max_ncbs As Integer
   xmit_buf_unavail As Integer
   max_dgram_size As Integer
   pending_sess As Integer
   max_cfg_sess As Integer
   max_sess As Integer
   max_sess_pkt_size As Integer
   name_count As Integer
End Type
Private Type NAME_BUFFER
   name As String * NCBNAMSZ
   name_num As Integer
   name_flags As Integer
End Type

'when NCBASTAT is specified, the
'ncb_buffer member of NET_CONTROL_BLOCK
'points to a buffer to be filled with
'an ADAPTER_STATUS structure, followed
'by an array of NAME_BUFFER structures
Private Type ASTAT
   NameBuff(0 To 30) As NAME_BUFFER
End Type

Private Declare Function Netbios Lib "netapi32.dll" _
  (pncb As NET_CONTROL_BLOCK) As Byte
Private Declare Sub CopyMemory Lib "kernel32" _
   Alias "RtlMoveMemory" _
  (hpvDest As Any, ByVal _
   hpvSource As Long, ByVal _
   cbCopy As Long)
Private Declare Function GetProcessHeap Lib "kernel32" () As Long

Private Declare Function HeapAlloc Lib "kernel32" _
  (ByVal hHeap As Long, _
   ByVal dwFlags As Long, _
   ByVal dwBytes As Long) As Long
Private Declare Function HeapFree Lib "kernel32" _
  (ByVal hHeap As Long, _
   ByVal dwFlags As Long, _
   lpMem As Any) As Long

Private Sub Form_Load()

   Command1.Caption = "Enum Lanas and Addresses"
End Sub

Private Sub Command1_Click()

   Dim cnt As Long
   Dim numLanas As Long
   Dim sMACAddresses() As String
  'get an array of strings containing the
  'MAC addresses of each NetBIOS-enabled
  'adapter, returning the number of adapters
  'in the array.
  'in calling, also pass the character you
  'want as a delimiter between MAC
  'address members
   numLanas = GetNBMacAddresses(sMACAddresses(), " ")  
   If numLanas > 0 Then
      List1.AddItem "Number of adapters: " & numLanas
      For cnt = 0 To numLanas - 1
         List1.AddItem ""
         List1.AddItem "MAC address of lana " & cnt & ":"
         List1.AddItem vbTab & sMACAddresses(cnt)
      List1.AddItem "No adapters using NetBIOS found"
   End If

End Sub

Private Function GetNBMacAddresses(sMACAddresses() As String, sDelimiter As String) As Long

  'retrieve the MAC addresses for all
  'installed and enabled network controllers
  'bound to the NetBIOS protocol.
   Dim cnt As Long
   Dim pASTAT As Long
   Dim buff As String
   Dim lana As LANA_ENUM  'enum values
   Dim ast As ASTAT
  'Enumerate LAN adapter (LANA) numbers.
  'When NCBENUM is specified the ncb_buffer
  'member points to a buffer to be filled
  'with a LANA_ENUM structure. NCBENUM is
  'not a standard NetBIOS 3.0 command.
   With ncb
      .ncb_command = NCBENUM
      .ncb_length = LenB(lana)
      .ncb_buffer = VarPtr(lana)
   End With
   Call Netbios(ncb)
  'instead of testing the return value of
  'the NetBIOS call as with other APIs, we
  'instead check the retcode member of the
  'NCB structure
   If ncb.ncb_retcode = NRC_GOODRET Then

     'prepare the array to receive
     'all MAC addresses, 0-based
      ReDim sMACAddresses(0 To lana.length - 1)
      For cnt = 0 To lana.length - 1
        'Reset the adapter - required
        'before it can accept any other
        'NCB command. The ncb_lana_num
        'member is assigned the next
        'lana number returned from the
        'NCBENUM call.
         With ncb
            .ncb_command = NCBRESET
            .ncb_lana_num = lana.adapter_numbers(cnt)
         End With
         Call Netbios(ncb)
         If ncb.ncb_retcode = NRC_GOODRET Then
           'To get the MAC address for an
           'ethernet adapter use send the
           'NCBASTAT command and provide
           '"*" as ncb_CallName (must be
           'formatted as a 16-chr string).
           'The same lana number is used.
            With ncb
               .ncb_command = NCBASTAT
               .ncb_lana_num = lana.adapter_numbers(cnt)
               .ncb_length = Len(ast)
               .ncb_callname = Space$(16)
               Mid$(.ncb_callname, 1, 1) = "*"
            End With
           'allocate memory for the ASTAT struct
            pASTAT = HeapAlloc(GetProcessHeap(), _
                               HEAP_GENERATE_EXCEPTIONS Or _
                               HEAP_ZERO_MEMORY, _
            If pASTAT <> 0 Then
              'assign the memory buffer to
              'the NCB buffer, call, and
              'copy the result to an AST type
               ncb.ncb_buffer = pASTAT
               Call Netbios(ncb)
               If ncb.ncb_retcode = NRC_GOODRET Then
                 'copy the info from the
                 'buffer into the UDT
                  CopyMemory ast, ncb.ncb_buffer, Len(ast)
                 'convert the byte array to a string
                  sMACAddresses(cnt) = MakeMacAddress(ast.adapt.adapter_address(), sDelimiter)
                  HeapFree GetProcessHeap(), 0, pASTAT
               End If  'ncb.ncb_retcode = NRC_GOODRET (NCBASTAT call)
               Debug.Print "HeapAlloc memory allcoation failed!"
            End If  'pastat
         End If  'ncb.ncb_retcode
      Next  'cnt
     'return number of adapters enumerated
      GetNBMacAddresses = lana.length
   End If  'ncb.ncb_retcode

End Function

Private Function MakeMacAddress(b() As Byte, sDelim As String) As String

   Dim cnt As Long
   Dim buff As String
   On Local Error GoTo MakeMac_error
  'so far, MAC addresses are
  'exactly 6 segments in size (0-5)
   If UBound(b) = 5 Then
     'concatenate the first five values
     'together and separate with the
     'delimiter char
      For cnt = 0 To 4
         buff = buff & Right$("00" & Hex(b(cnt)), 2) & sDelim
     'and append the last value
      buff = buff & Right$("00" & Hex(b(5)), 2)
   End If  'UBound(b)
   MakeMacAddress = buff
   Exit Function
   MakeMacAddress = "(error building MAC address)"
   Resume MakeMac_exit
End Function


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