Resets all HTTP Headers, Cookies, LocalFile , and AttachedFile .
The 'callback' parameter specifies a function which will be called when the operation completes (or an error is encountered). If the 'callback' parameter is not specified, then the method will block and will not return until the operation completes (or an error is encountered).
The callback for this method is defined as:
'err' is the error that occurred. If there was no error, then 'err' is 'null'.
'err' has 2 properties which hold detailed information:
This method resets all the HTTP Headers as well as LocalFile and AttachedFile to "" (empty string). It also resets the Cookie properties. Use this method before creating a new request, so that headers from the previous message are not carried over to the next one.