https://en.wikipedia.org/wiki/Comet_(programming) is browsers holding an infinitely loading frame, so each client held open a connection for several hours. usually we included <script> tags in that infinitely loading frame so the events could do whatever instead of just adding more text somewhere off the screen below the current scroll position. an alternative way to do comet is to close the connection when there's an event and have the client reload the frame

nowadays people use websockets for comet

yeah, protothreads type stuff and pool allocators are great fits for that kind of work