A few months ago, the project I was working on came to a little dilemma. The system was built using AS2 (not my decision of course), and was using a mix of web services(ws) and an XMLSocket to communicate. The ws calls would be outgoing, and the XMLSocket would be incoming, that way the server could push any changes done on the back-end and the UI would then appropriately display the proper information.
Our dilemma came when the manager of the project then wanted the application to be accessed from behind any firewall as long as http requests are accepted behind that firewall (as in, a corporate firewall). Since XMLSocket doesn’t do http request, it would of been filtered out and our system wouldn’t work at all. While looking for the solution, we found BlazeDS, an open source solution from Adobe. It’s a Java library that let’s you do remoting and web messaging using various different protocols. They have a pushing solution that works over port 80 with http request. Perfect.
