The following code (from the examples) accepts a connection and calls the handler handle_accept(). But it calls the handler only if the connection attempt (internally) succeeds. The handler gets not called if the connection fails (for example when an ssl-connection-attempt fails due to wrong keys etc.). What should I do to get informed also about such failed connection attempts? acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error));