How do I make a ROS2 node communicate with a remote ROS2 node network?

edit

If the nodes are running on separate machines, but are in the same network, you can just use the ROS_DOMAIN_ID as a unique identifier of the ROS_DOMAIN they should use to communicate.

So, from both the machines, export the ROS_DOMAIN_ID as an environment variable, which will be used as a identifier.

For example, run the following command on both the machines.

export ROS_DOMAIN_ID=42

And you should now be able to list / echo / publish / subscribe, to ROS Topics easily.

For separate networks, I am not sure how it will work. Never tried.