GMS Http Callback Notification

[Daere]

Hi all!

Into the GMS Deployment Guide it's indicated that the parameter customhttp.url allow to send a push notification through an HTTP url to another server (e.g. Microsoft Azure). It's correct?
With this configuration, the client must implements the CometD protocol or not?
Considered that the subscription to the ORS it's the first step to initiate a chat interaction, in this scenario, I must implement this first registration step or not?

Thanks