My understanding of Comet is that its a server-side AJAX request. My understanding of Long Polling ("Push") is that it is also a server-side AJAX request. My understanding of WebSockets is that they are a two-way AJAX request.
If any of these are wrong, please begin by correcting me!
Assuming I'm more or less correct, is it true that these are all just AJAX (JavaScript using XmlHttpRequest object under the hood)? If they are not all just AJAX calls, then how do you implement them in the client (via JavaScript) and on the server (using something like Java)? Thanks in advance!
Your understanding of WebSockets is incorrect. WebSockets is a new protocol and provides a new API that has nothing to do with XmlHttpRequest.
This is how you create a WebSocket
var exampleSocket = new WebSocket(
"ws://www.example.com/socketserver", "protocolOne"
);