Idle Musings of a Delphi Junkie

I needed to enumerate all the available COM ports in a .NET application I was writing the other day. Because the 1.1 version of the .NET Framework has no inbuilt support for serial communications, this meant it was time to Google a solution. To my surprise there were surprisingly few hits, with the only usable solution described on a web site written in Chinese. Not to be discouraged, I used the AltaVista BabelFish translation service to translate it to English, and below is the end result (after converting it from C# with the help of the Borland BabelCode web service). I customized it slightly so that either all ports on the system would be returned, or only COM ports (which is all that I was interested in at the time). I'm posting this here so an easy solution will be a mere Google away for all those English speaking Delphi programmers out there. :-)

unit AvailablePortsUnit;

interface

uses
  System.Runtime.InteropServices, System.Collections.Specialized;

type
  [StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]
  PORT_INFO_1 = record
    pName: string;
  end;

function AvailablePorts(const AComPortsOnly: Boolean): StringCollection;

implementation

[DllImport('winspool.drv', CharSet=CharSet.Auto)]
function EnumPorts(AName: string; ALevel: Integer; ABuffer: IntPtr;
      ACbBuff: Integer; out ANeeded: Integer; out AReturned: Integer): Boolean; external;

function AvailablePorts(const AComPortsOnly: Boolean): StringCollection;
type
  TPortInfoArray = array of PORT_INFO_1;
var
  lIndex: Integer;
  lComName: string;
  i: Integer;
  lCurrent: IntPtr;
  lPorts: TPortInfoArray;
  lBuffer: IntPtr;
  lNeeded: Integer;
  lReturned: Integer;
begin
  Result := StringCollection.Create;
  lBuffer := IntPtr.Zero;
  EnumPorts(nil, 1, lBuffer, 0, lNeeded, lReturned);
  lBuffer := Marshal.AllocHGlobal((lNeeded + 1));
  try
    EnumPorts(nil, 1, lBuffer, lNeeded, lNeeded, lReturned);
    SetLength(lPorts, lReturned);
    lCurrent := lBuffer;
    for i := 0 to lReturned - 1 do
    begin
      lPorts[i] := (PORT_INFO_1(Marshal.PtrToStructure(lCurrent, TypeOf(PORT_INFO_1))));
      if (not AComPortsOnly) or (lPorts[i].pName.StartsWith('COM')) then
      begin
        if AComPortsOnly then
        begin
          lIndex := lPorts[i].pName.IndexOf(':');
          if (lIndex <> -1) then
            lComName := lPorts[i].pName.Remove(lIndex, 1)
          else
            lComName := lPorts[i].pName;
        end
        else
          lComName := lPorts[i].pName;
        Result.Add(lComName);
      end;
      lCurrent := IntPtr((Integer(lCurrent) + Marshal.SizeOf(TypeOf(PORT_INFO_1))));
    end;
  finally
    Marshal.FreeHGlobal(lBuffer);
  end;
end;
end.