Android GCM SENDER_ID, how to get it?

Question

I try to migrate to GCM and I have an issue with the SENDER_ID I need to provide. I use the demo project from google. In this project I need, if I

Answer 1

If you came here because you are doing web push, Android push, or the like, there is a different answer.

Source: https://firebase.google.com/docs/cloud-messaging/js/client