http://async-io.org/

The Atmosphere Framework contains client and server side components for building Asynchronous Web Applications. The majority of popular frameworks are either supporting Atmosphere or supported natively by the framework. The Atmosphere Framework supports all major Browsers and Servers.

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Atmosphere transparently supports WebSockets, Server Side Events (SSE), Long-Polling, HTTP Streaming (Forever frame) and JSONP.

The Atmosphere Framework Stack consists of:

The Atmosphere Framework Stack works on all Servlet based servers including Tomcat, JBoss Jetty, Resin, GlassFish, Undertow, WebSphere, WebLogic etc. Not running a Servlet Container? Netty, Play! Framework orVert.x. We support a variety of extensions like STOMP, Redis, Hazelcast, JMS, JGroups and many more. Support for Socket.IO, SockJS and Cometd are also available.

Using another framework? Look at the list of supported extensions. Easiest way to learn Atmosphere is by trying a sample.

Atmosphere's Java/Scala/Android Client is called wAsync.