Program security using mac id in vb6

Option Explicit
' net config workstation

' from NB30.h

'#define NCBNAMSZ        16    /* absolute length of a net name           */
'#define MAX_LANA       254    /* lana's in range 0 to MAX_LANA inclusive */
'#define NCBENUM         0x37            /* NCB ENUMERATE LANA NUMBERS         */

Private Const NCBNAMSZ = 16
Private Const MAX_LANA = 254

Private Const NCBRESET = &H32
Private Const NCBASTAT = &H33
Private Const NCBENUM = &H37

Private Type NCB
    ncb_command As Byte ' APIViewer defines this incorrectly as Integer
    ncb_retcode As Byte ' APIViewer defines this incorrectly as Integer
    ncb_lsn As Byte ' APIViewer defines this incorrectly as Integer
    ncb_num As Byte ' APIViewer defines this incorrectly as Integer
    ncb_buffer As Long ' APIViewer defines this incorrectly as String
    ncb_length As Integer
    ncb_callname As String * NCBNAMSZ
    ncb_name As String * NCBNAMSZ
    ncb_rto As Byte ' APIViewer defines this incorrectly as Integer
    ncb_sto As Byte ' APIViewer defines this incorrectly as Integer
    ncb_post As Long
    ncb_lana_num As Byte ' APIViewer defines this incorrectly as Integer
    ncb_cmd_cplt As Byte  ' APIViewer defines this incorrectly as Integer
    ncb_reserve(0 To 9) As Byte ' Reserved, must be 0, ' APIViewer defines this incorrectly as (10)
    ncb_event As Long
End Type

Private Type LANA_ENUM
        Length As Integer
        Lana(0 To MAX_LANA) As Integer
End Type

'#define NRC_GOODRET     0x00    /* good return                                */
Private Const NRC_GOODRET = 0

Private Declare Function Netbios Lib "netapi32.dll" (pncb As NCB) As Byte

Private Type ADAPTER_STATUS
    adapter_address(0 To 5) As Byte             'As String * 6
    rev_major As Byte           ' APIViewer defines this incorrectly as Integer
    reserved0 As Byte           ' APIViewer defines this incorrectly as Integer
    adapter_type As Byte         ' APIViewer defines this incorrectly as Integer
    rev_minor As Byte           ' APIViewer defines this incorrectly as Integer
    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

Private Type ASTAT
     adapt As ADAPTER_STATUS
     NameBuff(30) As NAME_BUFFER        ' ?? 30 or 0 to 29 aod
End Type

   

' From MSDN Q118623 HOWTO: Get the MAC Address for an Ethernet Adapter

Public Function LANA_List() As Variant
    Dim NCB As NCB
    Dim LANA_ENUM As LANA_ENUM

'      Ncb.ncb_command = NCBENUM;
    NCB.ncb_command = NCBENUM
    
'      Ncb.ncb_buffer = (UCHAR *)&lenum;
    NCB.ncb_buffer = VarPtr(LANA_ENUM)
'      Ncb.ncb_length = sizeof(lenum);
    NCB.ncb_length = Len(LANA_ENUM)
    
'      uRetCode = Netbios( &Ncb );
    Dim Ret As Byte
    Ret = Netbios(NCB)
    If Ret <> NRC_GOODRET Then
        Err.Raise 5, , "LANA_lst: Error from Netbios, return code = " & Ret
    End If
    
    ' copy array to a nice variant array. VB Style
    If LANA_ENUM.Length > 0 Then
        ReDim List(LANA_ENUM.Length - 1)
    
        Dim Index As Long
        For Index = 0 To LANA_ENUM.Length - 1
           List(Index) = LANA_ENUM.Lana(Index)
        Next Index
        LANA_List = List
    Else
        LANA_List = Array()
    End If
End Function


Public Function MacAddress(ByVal LANA_Number_IN As Long) As String
    Dim NCB As NCB
    Dim Ret As Byte
    
    NCB.ncb_command = NCBRESET
    Ret = Netbios(NCB)
    If Ret <> NRC_GOODRET Then
        Err.Raise 5, , "MacAddress: Error from Netbios, return code = " & Ret
    End If
    
    NCB.ncb_command = NCBASTAT
    NCB.ncb_lana_num = LANA_Number_IN
    NCB.ncb_callname = "*"
    Debug.Assert NCB.ncb_callname = "*               "
    
    Dim ASTAT As ASTAT
    NCB.ncb_length = Len(ASTAT)
    Debug.Assert NCB.ncb_length = 680
    NCB.ncb_buffer = VarPtr(ASTAT)
    Ret = Netbios(NCB)
    If Ret <> NRC_GOODRET Then
        Err.Raise 5, , "MacAddress: Error from Netbios, return code = " & Ret
    End If
    
    ' this should be returned as an array of bytes someday
    MacAddress = Hex(ASTAT.adapt.adapter_address(0)) & " " & _
           Hex(ASTAT.adapt.adapter_address(1)) _
           & " " & Hex(ASTAT.adapt.adapter_address(2)) & " " _
           & Hex(ASTAT.adapt.adapter_address(3)) _
           & " " & Hex(ASTAT.adapt.adapter_address(4)) & " " _
           & Hex(ASTAT.adapt.adapter_address(5))
    'Debug.Print MacAddress
End Function


Sub main()
    Dim Lana As Variant
    
    ' this will return multiple LANA when connected to a dial up connection & a NIC
    For Each Lana In LANA_List
        Debug.Print Lana, MacAddress(Lana)
    Next Lana
End Sub