How to retrieve a file from Internet via HTTP?

Question

I want to download a file from Internet and InternetReadFile seem a good and easy solution at the first glance. Actually, too good to be true. Indeed, digging a bit I have s

Answer 1

Here's some sample code that uses Indy. This code is for Delphi 2010 (with Indy 10?), but the code for Delphi 7 would be similar. I've used Indy for years with D7 and have been very happy with it. I think in D7 we use Indy 9. Check if you need to download a new version...

You can use OnWork and OnWorkBegin to add a progress meter if you need to.

This code I excerpted from a bigger piece, editing it a bit. I did not try compiling it, but it will give you a good starting place.

function Download( const aSourceURL: String;
                   const aDestFileName: String;
                   out   aDownloadResult: TDownloadResult;
                   out   aErrm: String): boolean;
var
  Stream: TMemoryStream;
  IDAntiFreeze: TIDAntiFreeze;
begin
  aDownloadResult := DROther;
  Result := FALSE;
  fIDHTTP := TIDHTTP.Create;
  fIDHTTP.HandleRedirects := TRUE;
  fIDHTTP.AllowCookies := FALSE;
  fIDHTTP.Request.UserAgent := 'Mozilla/4.0';
  fIDHTTP.Request.Connection := 'Keep-Alive';
  fIDHTTP.Request.ProxyConnection := 'Keep-Alive';
  fIDHTTP.Request.CacheControl := 'no-cache';
  IDAntiFreeze := TIDAntiFreeze.Create;

  Stream := TMemoryStream.Create;
  try
    try
      fIDHTTP.Get(aSourceURL, Stream);
      if FileExists(aDestFileName) then
        DeleteFile(PWideChar(aDestFileName));
      Stream.SaveToFile(aDestFileName);
      Result := TRUE;
      aDownloadResult :=drSuccess;
    except
      On E: Exception do
        begin
          Result := FALSE;
          aErrm := E.Message + ' (' + IntToStr(fIDHTTP.ResponseCode) + ')';
        end;
    end;
  finally
    Stream.Free;
    IDAntiFreeze.Free;
    fIDHTTP.Free;
  end;
end;  { Download }