HTTP2-compliant wrapper for sending iOS and Android push notifications

Defines publically-exposed Apple Push Notification Service (APNS) functions. For implementation see APNSWorker

Defines APNS notification struct and convenience constructor functions

Handles all APNS request and response parsing over an HTTP2 connection

Handles all Google Cloud Messaging (GCM) request and response functionality

Defines GCM notification struct and convenience constructor functions

Contains shared functions for GCM and APNS

Supervises an APNSWorker, restarting as necessary