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Wininet downloading file .When I start with downloading my project is blocked (freezed).

Posted on 2003-10-25
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Last Modified: 2010-04-03
I use Wininet lib. for downloading file from internet. When I start with downloading my project is blocked (freezed).
How can i fix this problem?

I use this method for downloading file:

{
var
hInternetO,hHInternetC,hResource:HINTERNET;
FileStream:TFileStream;
DataProceed:array[0..1023] of Char;
NumRead,i:Cardinal;
kraj:Boolean;
begin

  hInternetO:=InternetOpen( 'Naslov',INTERNET_OPEN_TYPE_PRECONFIG,nil,nil,0 );
  hHInternetC:=InternetConnect( HInternetO,PAnsiChar(Host),INTERNET_DEFAULT_HTTP_PORT,nil,nil,INTERNET_SERVICE_HTTP,0,0);
  hResource := HttpOpenRequest(hHInternetC, 'GET', PChar(Resource), nil, nil, nil, 0, 0);
  HttpSendRequest(hResource, nil, 0, nil, 0);

  ///
   try
     FileStream := TFileStream.Create('c:\', FileOpenModes[FileExists('c:\')]);
    except
     ShowMessage('Please enter valid URL !');
     Exit;
    end;
  try
    FileStream.Position := Result;
    repeat
      ZeroMemory(@DataProceed, SizeOf(DataProceed));

      InternetReadFile(hResource, @DataProceed, SizeOf(DataProceed)-1, NumRead);

      if (NumRead <= 0) then Break;
      FileStream.Write(DataProceed, NumRead);
      Result := Result + Integer(NumRead);

    until Kraj=true;
  finally
    FileStream.Free();
    InternetCloseHandle(hHInternetC);
    InternetCloseHandle(hInternetO);
  end;
}

Thank you.
0
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Question by:nikola_mk
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5 Comments
 
LVL 8

Accepted Solution

by:
gmayo earned 84 total points
ID: 9622495
It sounds as if the connection is "blocking". Try asynchronous operations - put INTERNET_FLAG_ASYNC in the flags, ie   hInternetO:=InternetOpen( 'Naslov',INTERNET_OPEN_TYPE_PRECONFIG,nil,nil,INTERNET_FLAG_ASYNC );

Geoff M.
0
 
LVL 12

Assisted Solution

by:Lee_Nover
Lee_Nover earned 83 total points
ID: 9623806
or put it in a thread - what I'd do
instead of all this code you can use URLDownloadToFile or Indy HTTP with Get
here's the code of my download unit


unit DownloadFileU;

{.$DEFINE UseIndy}

interface


function DownloadFile(const AURL, AFileName: string): Integer;

implementation

uses Classes, {$IFDEF UseIndy} IdHTTP, Windows; {$ELSE} Sysutils, UrlMon; {$ENDIF}

function DownloadFile(const AURL, AFileName: string): Integer;
{$IFDEF UseIndy}
var ms: TMemoryStream;
{$ELSE}

  function GetFileSize(const AFile: string): Integer;
  begin
       with TFileStream.Create(AFile, fmOpenRead) do
       try Result:=Size;
       finally Free; end;
  end;

{$ENDIF}
begin
     {$IFDEF UseIndy}
     with TIdHTTP.Create(nil) do
     try
        ms:=TMemoryStream.Create;
        try
           try
              Get(AURL, ms);
              ms.SaveToFile(AFileName);
              Result:=ms.Size;
           except
              Result:=-2;
           end;
        finally
           ms.Free;
        end;
     finally
        Free;
     end;
     {$ELSE}
     try
        if URLDownloadToFile(nil, PChar(AURL), PChar(AFileName), 0, nil) = 0 then
           Result:=GetFileSize(AFileName)
        else
           Result:=-1;
     except
        Result:=-2;
     end;
     {$ENDIF}
end;

end.
0
 
LVL 17

Assisted Solution

by:Wim ten Brink
Wim ten Brink earned 83 total points
ID: 9627642
Maybe do the download from a separate thread?
0

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