class connection_base {
public:
  // types
  typedef net::socket::socket          socket_base_t;              
  typedef boost::net::socket::socket_t os_socket_t;                
  typedef os_socket_t                  descriptor_t;               
  typedef boost::function0< void >     close_notification_function;  // close notifcation for control 

  // construct/copy/destruct
  connection_base(socket_base_t &);
  connection_base(connection_base &);

  // public member functions
  bool is_open() const;
  os_socket_t descriptor() const;
  void on_close_notification(const close_notification_function &) ;

  // protected member functions
  void has_closed() ;
};