AWS SNS GCM notification
GCM send notification to android device: https://docs.kii.com/cn/samples/push-notifications/push-notifications-android/ https://www.intertech.com/Blog/push-notifications-tutorial-for-android-using-google-cloud-messaging-gcm/
make a configuration file: https://pushbots.com/developer/docs/android-configuration or follow the instruction to use firebase
GCM TESTING: http://apns-gcm.bryantan.info/
TO register AWS SNS with GCM for testing(In this case, each phone has registered one by one): Set in aws sns web page
Option 1: 
Option 2: Use Code in SNSTestActivity: 'AWSCreateEndpointTask' End Point can be known through result
reference Link: http://www.mobileaws.com/2015/03/25/amazon-sns-push-notification-tutorial-android-using-gcm/
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Video reference: https://www.youtube.com/watch?v=XM3THjZkRQM