I didn't say that everything was a client/server type of interaction; I said that client/server interactions are more common than bi-directional client/client i

I didn't say that everything was a client/server type of interaction; I said that client/server interactions are more common than bi-directional client/client interactions. You've provided a list of client/client protocols, which is great, but I still think client/server is much more common. For client/client, you're right: HTTP is not appropriate. If you can stomach the XML Jabber (aka XMPP, right?) looked like a good general-purpose bi-directional protocol, and if I'm not mistaken that's what Google Wave is using. If you don't want to pay the XML parsing/serializing overhead, other protocols are available, and maybe that's why BERT-RPC was created. My original point was simply that, depending upon the requirements, the existing HTTP protocol might be sufficient for the kind of interaction needed and it's supported by a rich infrastructure.