Construct a descriptor without opening it.
template< typename ExecutionContext> basic_descriptor( ExecutionContext & context, typename constraint< is_convertible< ExecutionContext &, execution_context & >::value, defaulted_constraint >::type = defaulted_constraint());
This constructor creates a descriptor without opening it.
An execution context which provides the I/O executor that the descriptor will use, by default, to dispatch handlers for any asynchronous operations performed on the descriptor.