When an valid path string is supplied and it is allowed in file ACL list, 
    the WebDAV HTTP requests and responces will be logged in append mode in to that file.
    When an open logging session is encountered the second call will produce an error.
    Specifying a NULL instead of file_path string stops the logging.The log file consists of lines with following fields:The request and response are marked by <<< and 
      >>> signsClient IP addressDate and time of request/responseTimestamp (milliseconds)Request/response line