I'm building an Android app as part of a client/server architecture, where my server will provide a service to the Android client. The server will not communicate with any Google server, but will need to authenticate the user via their gmail account. That is, the server needs to be sure that the http(s) requests coming from the phone are indeed from the person with that specific gmail account.
I was looking into Android's C2DM framework, which I can certainly use for passing service-related data back and forth, but how can I use Google account authentication between an Android phone and a third-party (non-Google) server?
Will Oath2.0 work for this, or is Oath2.0 only used for direct authentication between the phone and Google's services?
You didn't mention which language code you're going to use in your server.
The easier way to use C2DM is inside Google App Engine which comes with native support for Android integrations with C2DM.
If that's not the case ( EX: youre using php in your own server ) I would take a look to AccountManager which can provides you the auth token ( the app-user must allow it ).
When registering a new device to your C2DM server you'll need the device to communicate also the token so you'll be able to know if the user is really owner of that gmail account through a connection between your server and Google Servers.
:)