(Deprecated: Use non-error_code overload.) Run the io_context
object's event processing
loop to execute ready handlers.
count_type poll( asio::error_code & ec);
The poll()
function runs handlers that are ready to run, without blocking, until
the io_context
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.