Apache Tomcat - An open source software implementation of the Java Servlet and JavaServer Pages technologies
simperium - Move data everywhere it's needed, instantly and automatically
Spring Framework - The Spring Framework provides a comprehensive programming and configuration model for modern Java-based enterprise applications - on any kind of deployment platform.
GUN - Self-hosted Firebase.
Eclipse Jetty - Jetty is a highly scalable modular servlet engine and http server that natively supports many modern protocols like SPDY and WebSockets.
PubNub - PubNub is a real-time messaging system for web and mobile apps that can handle API for all platforms and push messages to any device anywhere in the world in a fraction of a second without having to worry about proxies, firewalls or mobile drop-offs.