Asynchronously read messages and invoke a callback when they are ready.

        :param callback: A callback with the received data

def read_async(self):
        '''
        Asynchronously read messages and invoke a callback when they are ready.

        :param callback: A callback with the received data
        '''
        while not self.connected():
            try:
                yield self.connect(timeout=5)
            except tornado.iostream.StreamClosedError:
                log.trace('Subscriber closed stream on IPC %s before connect', self.socket_path)
                yield tornado.gen.sleep(1)
            except Exception as exc:
                log.error('Exception occurred while Subscriber connecting: %s', exc)
                yield tornado.gen.sleep(1)
        yield self._read_async(self.__run_callbacks)