This function uses the SIZE command to determine the length of the
specified file. Not all servers implement this command, in which case
the function call will fail, and the lpdwFileSize parameter
will be set to zero.
Note that if the file on the server is a text file, it is possible
that the value returned by this method will not match the size of the
file when it is downloaded to the local system. This is because
different operating systems use different sequences of characters to
mark the end of a line of text, and when a file is transferred in
text mode, the end of line character sequence is automatically
converted to a carriage return-linefeed, which is the convention used
by the Windows platform.
Some FTP servers will refuse to return the size of a file if the
current file type is set to FILE_TYPE_ASCII because the size of
a text file on the server may not accurately reflect what the size of
the file will be on the local system.