How do android chat apps using GCM work?

Question

I want to create a simple chat app for learning purposes.

This mentions a "3rd-party app server" but what's its purpose?

To my understanding this is it:

• Android device registers its registration id with the 3rd-party server
• Android device sends messages to the 3rd party server
• 3rd-party server sends these messages to Google Cloud messaging using HTTP or XMPP
• GCM respond and the 3rd-party servers sends them back to the client

Is any part of this correct?

Answer 1

This mentions a "3rd-party app server" but what's its purpose?

Since you are the one who creates the server, that is up to you.

Is any part of this correct?

Your fourth bullet should be:

• GCM delivers the messages from the preceding bullet down to the requested device(s) and your app on them

Otherwise, your description seems accurate.