How different is server-side coding?
Since there is not much difference, you can just check out most of the example server-side codes for GCM as well. Main difference with regards to GCM and FCM is that when using FCM, you can use the new features with it (as mentioned in this answer). FCM also has a Console where you can send the Message/Notification from, without having your own app server.
NOTE: Creating your own app server is up to you. Just stating that you can send a message/notification via the console.
The URL used is "https://android.googleapis.com/gcm/send". What would be the equivalent URL for FCM?
The equivalent URL for FCM is https://fcm.googleapis.com/fcm/send. You can check out the this doc for more details.
Cheers! :D
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…