|  | 
            Run the io_service
            object's event processing loop to execute ready handlers.
          
std::size_t poll( asio::error_code & ec);
            The poll()
            function runs handlers that are ready to run, without blocking, until
            the io_service
            has been stopped or there are no more ready handlers.
          
Set to indicate what error occurred, if any.
The number of handlers that were executed.