Question

I would like to use a unique identifier to determine whether my application moved to a different computer. The MAC address seems to be suitable for this purpose. The code I use is this:

Procedure TForm4.GetMacAddress;
var item: TListItem;
    objWMIService : OLEVariant;
    colItems      : OLEVariant;
    colItem       : OLEVariant;
    oEnum         : IEnumvariant;
    iValue        : LongWord;
    wmiHost, root, wmiClass: string;
    i: Int32;

  function GetWMIObject(const objectName: String): IDispatch;
  var
    chEaten: Integer;
    BindCtx: IBindCtx;//for access to a bind context
    Moniker: IMoniker;//Enables you to use a moniker object
  begin
    OleCheck(CreateBindCtx(0, bindCtx));
    OleCheck(MkParseDisplayName(BindCtx, StringToOleStr(objectName), chEaten, Moniker));//Converts a string into a moniker that identifies the object named by the string
    OleCheck(Moniker.BindToObject(BindCtx, nil, IDispatch, Result));//Binds to the specified object
  end;

begin
   wmiHost       := '.';
   root          := 'root\CIMV2';
   wmiClass      := 'Win32_NetworkAdapterConfiguration';
   objWMIService := GetWMIObject(Format('winmgmts:\\%s\%s',[wmiHost,root]));
   colItems      := objWMIService.ExecQuery(Format('SELECT * FROM %s',[wmiClass]),'WQL',0);
   oEnum         := IUnknown(colItems._NewEnum) as IEnumVariant;
   i := 0;
   while oEnum.Next(1, colItem, iValue) = 0 do
   begin
      Item := View.Items.Add;
      item.Caption := Copy (colItem.Caption, 2, 8);

      Item.SubItems.Add (colItem.Description);
      Item.SubItems.Add (colItem.ServiceName);
      Item.SubItems.Add (VarToStrNil (colItem.MACAddress));
      if (VarToStrNil(colItem.MACAddress) <> '')
         then Item.SubItems.Add ('yes')
         else Item.SubItems.Add ('no');
      if colItem.IPEnabled
         then Item.SubItems.Add ('yes')
         else Item.SubItems.Add ('no');
     Item.SubItems.Add (VarToStrNil (colItem.SettingID));
     Item.SubItems.Add (IntToStr (colItem.InterfaceIndex));
   end; // if
end; // GetMacAddress //

My machine has one network port, but this code finds 18 network related ports/things/whatever. Among them there are four MAC adresses. I presume that a network port should be IP enabled so that leaves two left (labeled MAC in the image). Is it correct to assume that of the ports thus filtered, the one with the lowest index is the hardware port?

Edit in the snapshot above the Realtek adapter is the only physical adapter in the machine. The other adapter is the VirtualBox virtual adapter. The answer of TLama identifies these two adapters, but is there a way to find the address of the only Physical (Realtek) adapter?

Update 1 EJP pointed out that the MAC address can be changed. This somewhat undermines my purpose, but as I am looking for a solution that fits most situations I decided to live with it.

TLama and TOndrej pointed to several solutions. Both end up with a situation that a physical adapter could not be found without any doubt.

Update 2 TLama’s excellent reading list shows that there is probably not a certain way to determine the physical adapter. The article mentioned in the first bullet shows how to shrink the amount of adapters based on some simple assumptions. The article in the third bullet shows how to select the adapter connected to the PCI bus, which is in fact exactly what I wanted to know. There are some weird exceptions mentioned in the article but I think this will provide an answer in most cases.

Thank you all for your contributions!

Answer 1

Use the Win32_NetworkAdapter class instead. It has the PhysicalAdapter member. The following example should list you the MAC addresses of physical adapters:

program Program1;

{$APPTYPE CONSOLE}

uses
  SysUtils, ActiveX, ComObj, Variants;

procedure GetWin32_NetworkAdapterInfo;
const
  WbemUser = '';
  WbemPassword = '';
  WbemComputer = 'localhost';
  wbemFlagForwardOnly = $00000020;
var
  ElementCount: LongWord;
  FWMIService: OleVariant;
  FWbemObject: OleVariant;
  EnumVariant: IEnumVARIANT;
  FSWbemLocator: OleVariant;
  FWbemObjectSet: OleVariant;
begin;
  FSWbemLocator := CreateOleObject('WbemScripting.SWbemLocator');
  FWMIService := FSWbemLocator.ConnectServer(WbemComputer, 'root\CIMV2', WbemUser, WbemPassword);
  FWbemObjectSet := FWMIService.ExecQuery('SELECT * FROM Win32_NetworkAdapter WHERE PhysicalAdapter = 1', 'WQL', wbemFlagForwardOnly);
  EnumVariant := IUnknown(FWbemObjectSet._NewEnum) as IEnumVariant;
  while EnumVariant.Next(1, FWbemObject, ElementCount) = 0 do
  begin
    Writeln(Format('MACAddress %s', [VarToStr(FWbemObject.MACAddress)]));
    FWbemObject := Unassigned;
  end;
end;

begin
  try
    CoInitialize(nil);
    try
      GetWin32_NetworkAdapterInfo;
    finally
      CoUninitialize;
    end;
  except
    on E:EOleException do
      Writeln(Format('EOleException %s %x', [E.Message,E.ErrorCode]));
    on E:Exception do
      Writeln(E.Classname, ':', E.Message);
  end;
  Writeln('Press Enter to exit');
  Readln;
end.

Based on the code generated by the WMI Delphi Code Creator.

Update:

You are actually trying to filter out the adapters which belongs to virtual machines, what is not that easy since they are simulated like to be as physical ones (you can even see them in Device Manager as the physical adapters), so you cannot distinguish them e.g.:

• by the DHCPEnabled member of the Win32_NetworkAdapter class, because even virtual machines might be configured so they get IP address from a DHCP server
• by the AdapterTypeId member of the Win32_NetworkAdapter class, since there is no special type for virtual adapters
• by the PhysicalAdapter member of the Win32_NetworkAdapter class, because they are being simulated to be physical

Additional reading:

• Find only physical network adapters with WMI Win32_NetworkAdapter class – this article has a good analysis and it might fulfill your needs (I haven’t tested it though)

• How to determine physical network adapter type using WMI – this question is opened at this time and it is actually exactly what you need

• How to determine MAC Address of the physical network card – there is one idea I like and I would personally stick to when I’d be 100% sure that the root of the PNPDeviceID member
  of the Win32_NetworkAdapter class for hardware adapters cannot start with something different from the PCI\\ (actually the same I was thinking about when I was comparing the data)