|  | 
            (Deprecated: Use non-error_code overload.) Run the io_context object's event processing
            loop to execute at most one handler.
          
count_type run_one( asio::error_code & ec);
            The run_one()
            function blocks until one handler has been dispatched, or until the
            io_context
            has been stopped.
          
            The number of handlers that were executed. A zero return value implies
            that the io_context
            object is stopped (the stopped() function returns true).
            Subsequent calls to run(), run_one(), poll() or poll_one() will return immediately unless there
            is a prior call to restart().
          
The number of handlers that were executed.
            Calling the run_one()
            function from a thread that is currently calling one of run(),
            run_one(),
            run_for(),
            run_until(),
            poll()
            or poll_one()
            on the same io_context
            object may introduce the potential for deadlock. It is the caller's reponsibility
            to avoid this.