Shut down SSL on the stream.
asio::error_code & ec);
This function is used to shut down SSL on the stream. The function call
will block until SSL has been shut down or an error occurs.
Set to indicate what error occurred, if any.
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)