Are you using two applications running in isolated ROS 2 domain IDs? Do you need to bridge topics between the applications?
eProsima Integration Service is an open source product that enables to bridge two ROS 2 dataspaces easily.
Integration Service allows a ROS 2 publisher application, running under a certain domain ID, to communicate with a ROS 2 subscriber (echo) application, which is running under a different domain ID. Follow step-by-step here.
Integration Service is configured by means of a YAML text file, through which the user can provide a mapping between the topics and services handled by the middlewares of the systems involved.
Check the Integration Service Manual and examples in the Integration Service doc page.