def open(self):
        """
        Called on new websocket connection.
        """
        sess_id = self._get_sess_id()
        if sess_id:
            self.application.pc.websockets[self._get_sess_id()] = self
            self.write_message(json.dumps({"cmd": "status", "status": "open"}))
        else:
            self.write_message(json.dumps({"cmd": "error", "error": "Please login", "code": 401}))