Sending messages from one device directly to another device it not supported through Firebase Cloud Messaging. -- Frank van Pufflenen - JUNE 23 2016
That was quite some time ago, and there aren't any updates in the docs. However:
- Has there been any changes?
- Is Firebase the only option? Are there any other app servers (Like Firebase and the shut-down Parse)?
- I don't want to find/buy a server just for this. But is the Firebase Server SDK suitable for this?
- Can this be implemented using GCM?