I\'m sure Wave doesn\'t poll the server every millisecond to find out if the other user has typed something... so how can I see what the other person is typing as they type? And
They probably use Web Sockets, aka server-sent events: http://www.w3.org/TR/websockets The underlying protocol can be found (as a draft) at the IETF.
Update: it doesn't seem WebSockets has any implementation yet; and a video from Google I/O (go to 11:00) talks about a long lived HTTP GET request.