Ableton/link ? reverse-engineered prompt

Build me a small C++ library and example app for keeping music apps in sync over a local network, like Ableton Link.

I want the app to let multiple instances find each other automatically, stay on the same beat, keep the same tempo and phase, and let any instance start, stop, or change tempo without breaking the session. Please include a couple of simple example programs so I can see how to use it in practice, and make sure it can be built and run with a normal CMake workflow.

If there are any setup steps needed for dependencies or submodules, include those too, and make the build instructions easy to follow. Please also add basic tests or a simple way to verify the sync behavior is working. If you need to check current docs or best practices online, go ahead and do that.