Orbited
Orbited is an HTTP daemon that is optimized for long-lasting comet connections. It is designed to be easily integrated with new and existing applications. Orbited allows you to write real-time web applications, such as a chat room or instant messaging client, without using any external plugins like Flash or Java.
It can be installed as a windows service. The license is MIT.
MethodWorx
MethodWorx was developed out of this series of articles on Code Project. It has an Open Source license.
This is a packaged version of a
library the we used in some projects
to enable COMET polling or
Long-Polling within some of our
ASP.NET applications.
It uses an Asynchronous HTTP handler
to keep ASP.NET connections open to
wait for events to occur, enabling
real-time AJAX callbacks.
Lightstreamer
LightStreamer Moderato is free but not open source
WebSync
WebSync is a standards-compliant scalable Comet server for IIS using .NET. It's also available on demand as a hosted service. This is neither free nor Open Source, but does have a free trial.
Other
There are several more Open Source Comet projects:
- aspcomet The aim of this project is to develop a COMET implementation which does not require a custom server, but can run in native IIS.
- emerge toolkit. No project activity in quite some time.