communicating between ROS2 Eloquent and Foxy
I have two Raspberry Pi 4b (arm64) machines that need to communicate. I am able to get them talking with the demo examples (demo_nodes_cpp talker/listener) when they are both running Ubuntu 18.04.05 Server LTS/ROS2 Eloquent Elusor. When one is running Ubuntu 18.04.05 Server LTS/ROS2 Eloquent Elusor and the other is running Ubuntu 20.04.3/ROS2 Foxy Fitzroy, the demo examples fail to work. I understand that it is recommended to use the same ROS2 distro for the whole network of machines, but I have two relatively mature code development efforts that happened on different distros that now need to merge.
Are there environment variables or DDS configurations that I can modify to enable them to communicate across these two distributions?