...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 one ready handler.
count_type poll_one( boost::system::error_code & ec);
function runs at most one handler that is ready to run, without blocking.
Set to indicate what error occurred, if any.
The number of handlers that were executed.