I am trying to send a notification to the application on the android device of all active and inactive users from a server. What do i need to use? GCM? The notification needs to to appear to all devices where the app has been installed in android.
GCM is enough for your case. Maintain a user table which store the user register ID. Then you can send GCM message from your server to the indented users using the user register ID. See this GCM tutorial