Options for real-time web notifications and updates using Comet/XMPP vs WebSocket technologies on a Microsoft stack?

Question

I am scoping out the architectural options for a project that will render live updates (like Facebook) of user activities - logins, photos, etc. Two main UI components of this are an auto-updating scrolling area where new notifications will be listed (photos, etc.), and a toolbar that will update with things like updated message counts, etc.

The contenders for this are Jabber/Comet/XMPP-based and WebSocket technologies.

Comet camp:

• Pokein
• WebSync

WebSockets camp:

• Kaazing
• LightStreamer
• SuperWebSocket
• XSockets
• SignalR

Since this the existing infrastructure is a Microsoft stack, I would rather not introduce Java-based servers into the mix. Saying this, it leaves (a very attractive) WebSync (Comet), and SuperWebSocket (WebSockets). However the Pokein's DLL integration is fairly seamless into a .Net project as well.

Are there any more real production level WebSocket initiatives for .Net? Is it too early to adopt WebSockets on a Microsoft stack, and should I go in favor of something like Kazing?

I am still waiting for a report on our current user base's browser types and versions (checking for HTML5 compatibility). I am suspecting that this number will be low (older user base). If that is the case, the Comet option would be the winner.

What are some other things to consider?

Looking at some of the .Net initiatives like Sockets.IO and others, I'm thinking this may be too much in its infancy yet, to apply to a large scale production system.

Can I get some comments from anyone that has used any of the technologies and products listed above?

Thanks.

UPDATE

I am still hunting for some good WebSocket servers that are reliable on a production level. I added XSockets and SignalR to the Websockets camp after recently finding them. Hoewver, there are still two main contenders at this time. That could be just because of the fact that they have amazingly great marketing teams, good material available for developers - API's, and videos. A lot of other implementations seem to still be in new-born phases, where examples are given of connectivity with only a few clients. While this demonstrates the technology, these demos are not backed up with significant payload/load capacity data. Kaazing and LightStreamer do meet the requirements below.

XSockets has some nice examples, but again, missing some real production metrics.

It doesn't seem that SignalR has yet been tested in a true production environment. A scale-out solution is in development but doesn't appear stable yet. Looking forward to seeing how this project does in the future.

Primary requirements are:

1. Ability to implement fallback technology (if HTML5/WebSockets are not available)
2. High number of concurrent connections and number of messages per second
3. Scalable - ability to add additional servers/nodes for larger traffic requirements

Answer 1

WebSync v4 uses WebSockets in addition to falling back to long-polling/callback-polling as needed. The WebSockets in WebSync are all over standard HTTP ports as well, so there won't be any issues with routers/filrewalls/etc.

On a "normal" system, you should see ~20k concurrent (per node) and ~100k messages/sec. Those are very rough numbers though, as it depends drastically on your system and the types of messages you're sending, etc. We've seen as high as 50k users (per node) and (in a different test) 300k messages/second.

(Disclaimer: I work for Frozen Mountain)