Socket.io Alternatives

The Jetty Web Server provides a HTTP server and Servlet container capable of serving static and dynamic contend either from a standalone or embedded instantiations.

JBoss is Red Hats Java EE 5-compliant (soon Java EE 6-compliant) application server. It is, as with Red Hat itself, dual-licensed either as open source (community edition) or commercially (enterprise edition).

gevent is a coroutine -based Python networking library that uses greenlet to provide a high-level synchronous API on top of the libev event loop.

Lightweight in-process concurrent programming.

Eventlet is a concurrent networking library for Python that allows you to change how you run your code, not how you write it.

Simperium is a service for developers to move data everywhere it's needed, instantly and automatically.

Pusher is a hosted API for quickly, easily and securely adding scalable realtime functionality to web and mobile apps.

Jet. Lightweight Realtime Message Bus for the Web.

A WebSocket Implementation for Node.JS ( Draft -08 through the final RFC 6455 ).

Lightstreamer is a server for delivering real-time messages to browser-based and mobile applications, using WebSockets and HTTP. Features include dynamic throttling, bandwidth and frequency control, delta delivery, and total control over security and the quality of service.