HOWTO: Using InternetReadFile To Get File

ID: Q149413

The information in this article applies to:

Microsoft Internet Explorer (Programming) version 3.0
Microsoft Internet Information Server version 3.0
Microsoft Windows NT, versions 3.51, 4.0, 4.0 SP4
Microsoft Windows 95

SUMMARY

Using a WinInet API, the InternetReadFile returns the following buffer:

<body><h1>HTTP/1.0 406 No acceptable objects were found</h1></body>

MORE INFORMATION

This is an HTTP server specific error. Microsoft IIS may return this error when there is no proper Accept header ("Accept: */*") in the HTTP request. Such a header can be added with following APIs:


   InternetOpenUrl(),
   HttpSendRequest(),
   HttpAddRequestHeaders()

Note that other HTTP servers may or may not behave in the same fashion. The following code demonstrates how to transfer any type of file with WinInet APIs:


   BOOL GetFile (HINTERNET IN hOpen, // Handle from InternetOpen()
                 CHAR *szUrl,        // Full URL
                 CHAR *szFileName)   // Local file name
   {
       DWORD dwSize;
       CHAR   szHead[] = "Accept: */*\r\n\r\n";
       VOID * szTemp[25];
       HINTERNET  hConnect;
      FILE * pFile;

       if ( !(hConnect = InternetOpenUrl ( hOpen, szUrl, szHead,
             lstrlen (szHead), INTERNET_FLAG_DONT_CACHE, 0)))
       {
         cerr << "Error !" << endl;
           return 0;
       }

       if  ( !(pFile = fopen (szFileName, "wb" ) ) )
      {
           cerr << "Error !" << endl;
          return FALSE;
      }
       do
       {
          // Keep coping in 25 bytes chunks, while file has any data left.
          // Note: bigger buffer will greatly improve performance.
          if (!InternetReadFile (hConnect, szTemp, 50,  &dwSize) )
          {
              fclose (pFile);
             cerr << "Error !" << endl;
            return FALSE;
          }
          if (!dwSize)
              break;  // Condition of dwSize=0 indicate EOF. Stop.
          else
             fwrite(szTemp, sizeof (char), dwSize , pFile);
       }   // do
      while (TRUE);
      fflush (pFile);
      fclose (pFile);
      return TRUE;
   }

The same task can be accomplished with WinInet MFC classes in following manner:


   #include <afx.h>
   #include <afxinet.h>

   BOOL  GetFile (CHAR *szUrl, CHAR *szFileName)
   {
   TCHAR sz[1024];
   CInternetSession session (_T("MyTest agent"), 1,
     INTERNET_OPEN_TYPE_DIRECT);
   CStdioFile* pFile = NULL;
   CHAR   szHead[] = "Accept: */*\r\n\r\n";
       DWORD nRead;
   CFile myFile;
   CFileException fileException;

   if ( !myFile.Open (szFileName, CFile::modeCreate | CFile::modeReadWrite,
      &fileException ) )
   {
   cerr << "Can't open file: " << szFileName
    << " error = " << fileException.m_cause  <<"\n";
   return FALSE;
   }

   try
   {
   pFile = session.OpenURL (szUrl, 1, INTERNET_FLAG_RELOAD
   |INTERNET_FLAG_TRANSFER_BINARY,
    szHead, -1L);

   }
   catch (CInternetException *pEx)
   {
   cerr <<"OpenUrl failed: "<< pEx-> m_dwError << endl;
   return FALSE;
   }

       do
   {
   nRead = pFile->Read(sz, 1023);
   if (nRead != 0)
   myFile.Write (sz, nRead);
   }
   while (nRead != 0);
   myFile.Close();
   pFile->Close();
   if (pFile != NULL)
   delete pFile;
   session.Close();
   return TRUE;
   }

Additional query words:

Keywords : kbnetwork kbprg kbIE300 kbWinInet
Version : WINDOWS:3.0,95; winnt:3.0,3.51,4.0,4.0 SP4
Platform : WINDOWS winnt
Issue type : kbhowto