Comet/Ajax-Push using CometD, APE etc on Shared Hosting?


I have been using a paid, shared hosting account on DreamHost to learn web development. So far I have learned how to write basic HTML/CSS, PHP, Javascript, and how to use MySQL, and also AJAX.

I am currently looking at AJAX Push technology, a.k.a. Comet. I am right to assume that if I want to use something like CometD or APE, I would need to upgrade my account to VPS?

Can AJAX Push be done using just DreamHost shared hosting? FYI I intend to get VPS in the near future, but would like to learn as much as possible on shared hosting first.