(Similar in spirit to but different in practice from this question.)

Is there any cross-browser-compatible, in-browser technology that allows a high-performance perstistent network connection between a server application and a client written in, say, Javascript? Think XmlHttpRequest on caffeine. I am working on a visualisation system that's restricted to at most a few users at once, and the server is pretty robust, so it can handle as much as it needs to. I would like to allow the client to have access to video streamed from the server at a minimum of about 20 frames per second, regardless of what their graphics hardware capabilities are.

Simply put: is this doable without resorting to Flash or Java?