Hi @Gaurnag,
Our old Companion Software is open source, so you can look at the code directly. On startup it runs the .companion.rc file, which is in charge of launching the appropriate services.
In case it’s helpful, I briefly described the services in this comment a couple of years ago. There’s also an overview diagram of the main software components and links, if that’s of interest.
That said, please be aware that the Companion Software is no longer being maintained or developed, and we recommend using BlueOS instead. Coincidentally, I’ve just recently added some initial development documentation for the latest version of BlueOS. Feel free to provide feedback if there’s anything you’d like more information about.