Are FCM and GCM backward and forward compatible?
问题 Google is deprecating Google Cloud messaging in favor of Firebase Cloud Messaging: Firebase Cloud Messaging (FCM) is the new version of GCM. It inherits the reliable and scalable GCM infrastructure, plus new features! See the FAQ to learn more. If you are integrating messaging in a new app, start with FCM. GCM users are strongly recommended to upgrade to FCM, in order to benefit from new FCM features today and in the future. From some tests I made on my servers, the FCM URL (https://fcm