|  | 
        A read handler must meet the requirements for a handler.
        A value h of a read handler
        class should work correctly in the expression h(ec,
        s),
        where ec is an lvalue of
        type const error_code
        and s is an lvalue of type
        const size_t.
      
A free function as a read handler:
void read_handler( const asio::error_code& ec, std::size_t bytes_transferred) { ... }
A read handler function object:
struct read_handler { ... void operator()( const asio::error_code& ec, std::size_t bytes_transferred) { ... } ... };
        A non-static class member function adapted to a read handler using bind():
      
void my_class::read_handler( const asio::error_code& ec, std::size_t bytes_transferred) { ... } ... socket.async_read(..., boost::bind(&my_class::read_handler, this, asio::placeholders::error, asio::placeholders::bytes_transferred));