I have been trying to get to the bottom of this problem off and on for the past 2 days and I'm really stuck. Hopefully some smart folks can help me out.

The issue is that I have a function that I call in a thread that downloads a file (using Synapse libraries) from a website that is passed to it. However, I've found that every once in a while there are sites where it will not pull down a file, but wget or Firefox/IE will download it without issue.

Digging into it, I've found some curious things. Here is the relevant code:

uses
//[..]
  HTTPSend,
  blcksock;

//[..]

type
  TMyThread = class(TThread)
  protected
    procedure Execute; override;
  private
    { Private declarations }
    fTheUrl: string;
    procedure GetFile(const TheUrl: string);
  public
    property thrd_TheUrl: string read fTheUrl write fTheUrl;
  end;

implementation

[..]

procedure TMyThread.GetFile(const TheUrl: string);
var
  HTTP: THTTPSend;
  success: boolean;
  sLocalUrl: string;
  IsSame : boolean;
begin

  HTTP := THTTPSend.Create;
  try
    HTTP.UserAgent :=
      'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727)';
    HTTP.ProxyHost := 'MYPROXY.COM';
    HTTP.ProxyPort := '80';

    sLocalUrl :=
      'http://web.archive.org/web/20071212205017/energizer.com/usbcharger/download/UsbCharger_setup_V1_1_1.exe';


   IsSame :=  SameText(sLocalUrl, sTheUrl); //this equals True when I debug

   ///
   ///
   /// THIS IS WHERE THE ISSUE BEGINS
   ///  I will comment out 1 of the following when debugging
   ///
    HTTP.HTTPMethod('GET', sLocalUrl); // ----this works and WILL download the file
    HTTP.HTTPMethod('GET', sTheUrl);  // --- this always fails, and HTTP.ResultString contains "Not Found"

    success := SysUtils.UpperCase(HTTP.ResultString) = 'OK';


    if HTTP.ResultCode > 0 then
      success := True; //this is here just to keep the value around while debugging
  finally
    HTTP.Free;
  end;
end;

procedure TMyThread.Execute
begin
   //fTheURL contains this value:  http://web.archive.org/web/20071212205017/energizer.com/usbcharger/download/UsbCharger_setup_V1_1_1.exe

   GetFile(fTheUrl);
end;

The problem is that when I assign a local variable to the function and give it the URL directly, everything works. However, when passing the variable into the function, it fails. Anyone have any ideas?

    HTTP.HTTPMethod('GET', sLocalUrl); // ----this works and WILL download the file
    HTTP.HTTPMethod('GET', sTheUrl);  // --- this always fails, and HTTP.ResultString contains "Not Found"

I'm using the latest version of Synapse from their SVN repository (version from 2 days ago).

NOTE: The file I am attempting to download is known to have a virus, the program I am writing is meant to download malicious files for analysis. So, don't execute the file once you download it.

However, I'm using this URL b/c this is the one I can reproduce the issue with.