Código Delphi [-]
Uses Printers;

Type
      TPrinterDevice = Class Driver, Device, Port: String;

TForm1.Button1Click(Sender:TObject);
Begin
    // Para obtener el nombre de la impresora.   
       Label1.Caption:= TPrinterDevice(Printer.Printers.Objects[Printer.PrinterIndex].Device;

    // Para obtener el tipo de puerto.   
       Label2.Caption:= TPrinterDevice(Printer.Printers.Objects[Printer.PrinterIndex].Port;
End;

Código Delphi [-]
uses WinSpool;
 
procedure TForm1.Button1Click(Sender: TObject);
var
 Size, Count, Index: Cardinal;
 Items: array [0..2047] of TPrinterInfo5;
 Default: array [0..255] of Char;
begin
 EnumPrinters(PRINTER_ENUM_LOCAL + PRINTER_ENUM_CONNECTIONS, nil, 5, @Items, SizeOf(Items), Size, Count);
 GetProfileString('windows', 'device', '', @Default, SizeOf(Default) - 1);
 Index := 0; while not (Default[Index] in [#0, ',']) do Inc(Index);
 Default[Index] := #0;
 for Index := 0 to Count - 1 do
  if not LongBool(lstrcmpi(@Default, Items[Index].pPrinterName)) then
   MessageBox(Handle, Items[Index].pPortName, nil, 0);
end;