Real-time bi-directional JSON-RPC communication over HTTP

I am building a JSON-RPC server that accepts requests over HTTP. I would like to support bi-directional communication (both client and server can send requests), the specific use case being a publish/subscribe architecture where a client sends a subscribe(X) request and receives changed(X) requests in (almost) real-time. As far as I know, there are several ways to implement this with HTTP:

• long polling
• WebSockets
• polling calls using a cookie-based session model
• streaming (keeping the HTTP connection open)
• a combination of some of the above

What I'm looking for is a solution that is based on accepted internet standards (if possible), usable from a web browser and easy to work with on the client side. So far, I favour the streaming thing (Twitter, CouchDB do it that way), but I'm not sure about how well this is supported within browsers and JSON-RPC libraries. Also, there may be other ways to do it that I'm not aware of.

Thank you in advance.

I think you should have a look at socket.io to accomplish your task. You could if you wanted to watch this video from the author: "Socket.IO Workshop: Guillermo Rauch". It is easy to work with on both server as client. I have created a simple sample pubsub using redis on top of socket.io.