...one of the most highly
regarded and expertly designed C++ library projects in the
world. — Herb Sutter and Andrei
(Deprecated: Use non-error_code overload.) Run the
io_context object's event processing
loop to execute ready handlers.
count_type poll( boost::system::error_code & ec);
function runs handlers that are ready to run, without blocking, until
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.