FTP and file opening

Hi everyone -

I am using VB6 to process files that are uploaded
from a device into a directory on a local machine.

My application looks into the FTP directory for new files
and as they are uploaded into the system, my application
opens the file and processes the contents.

The questions are....

1) Does standard windows IIS ftp service receives a file
from outside - does ftp open a file handle in the final directory
and copy byte by byte from the input stream???
OR
does ftp receive a file into a temporary location and after the
ftp copy is completed copy into the final location???

2) If the file is copied from a temporary location to the final
location - can another application open the file and read
the contents as they are being added to the file???


I am using binary lock read write against the file when i go to process
the contents -

sometimes it processes a zero length file - and i cannot find out
where the zero length file comes from -

the ftp log says the file is created with the correct file size.

anyone have any ideas????

thanks
tony