FTP WinInet APIs Report Error 12003

Symptoms  
  Connection   to   a   non-Microsoft   FTP   server   with   WinInet   FTP   APIs   may   fail   with   error   12003.         

Cause  
  When   connecting   to   a   non-Microsoft   FTP   server   with   WinInet   APIs,   some   WinInet   FTP   APIs   may  fail   with   error   12003   (ERROR_INTERNET_EXTENDED_ERROR).   The  InternetGetLastResponseInfo   API   may   not   retrieve   any   Internet   specific   information.   This   error   may   occur   when   the   FTP   server   sends   an   unexpected   status   code   to   the   WinInet   client.   Please   note   that   this   may   not   indicate   an   error,   but   rather   the   server's   success   message   or  confirmation   (such   as   confirmation   of   getting   a   file,   sending   a   directory   listing,   and   so   forth).   In   some   cases   the   WinInet   FTP   APIs   may   not   parse   such   messages   correctly   and   erroneously   report   an   error.   This   may   happen   when   the   WinInet   FTP   APIs   are   used   to   connect   to   certain   VAX/VMS   FTP   servers. 

Resolution  
  The   above   behavior   may   be   avoided   by   not   using   the   INTERNET_FLAG_PASSIVE   flag   in   the   InternetConnect   or   InternetOpenUrl   API.   When   this   flag   is   not   used   WinInet   uses   active   semantics   for   the   FTP   connection,   which   avoids   the   return   of   the   status   code,   which   causes   the   parsing   problem.