Open source push technology.

Z-Push is an open-source application to synchronize ActiveSync compatible devices such as mobile phones, tablets and Outlook 2013 and above. With a history of over 9 years of successful synchronization with multiple backends Z-Push is the leading open source push synchronization.

• Z-Push @ GitHub.

Open-source push notification service for developers. OneSignal alternative.

Effortlessly automate, track, and localize your push notifications with MagicPush. Seamlessly integrate with your website, iOS or Android apps using our simple libraries.

• MagicPush @ GitHub.

Send push notifications to your phone via PUT/POST.
ntfy (pronounce: notify) is a simple HTTP-based pub-sub notification service. It allows you to send notifications to your phone or desktop via scripts from any computer, entirely without signup, cost or setup. It's also open source if you want to run your own.

ntfy.sh @ GitHub

🚀 The open-source notifications infrastructure. A fully-featured microservice to send SMS, E-mail, Slack and Push notifications. Embeddable notification center for React with real-time updates, content management, and much more...
Notification management simplified.
The ultimate service for managing multi-channel notifications with a single API.

Create real-time web applications

Mobile data synchronization is becoming increasingly important for many people, and various standards have arisen to perform this two-way copying 'over-the-air'. The most important platforms that can do wireless synchronisation are ActiveSync that is used to communicate with Exchange Server and Research-in-Motion's BlackBerry Enterprise Server (BES).

If you are a native iPhone application developer, you may have heard of the Apple Push Notification service (APNs). There are a lot of excellent online guides on how to get your application to receive remote notifications... but what about the other piece of the puzzle... ACTUALLY SENDING A MESSAGE?!?!