What is it ? Most of the modern web applications display recently updated data, and to do that they need to get he latest data very frequently. Some of them even include some real-time chat (Gmail Chat, Facebook chat). How ? That’s the interesting part. Pull is pretty dumb. You do a request very frequently and you see if anything new appeared. This consumes some bandwidth, some resources (because server has to check if data has actually changed).
I’ve been working on a project where we had to use Flex on a .Net environment and it had to be realtime. I was a little worried at first that it could be tricky to set up. But with WebORB.Net it’s pretty easy. We used the integrated RTMP (Real Time Messaging Protocol) messaging server. It’s almost like using WCF. The most important differences are that, by default, objects are transmitted as Hashtable and calls can’t be synchronous.