|  | 
            Construct a posix::basic_descriptor on an existing
            native descriptor.
          
basic_descriptor( asio::io_service & io_service, const native_handle_type & native_descriptor);
This constructor creates a descriptor object to hold an existing native descriptor.
                  The io_service
                  object that the descriptor will use to dispatch handlers for any
                  asynchronous operations performed on the descriptor.
                
A native descriptor.
Thrown on failure.