I’ve gotten a lot of use out of network packet sniffers recently, in watching the AMF packets travel back and forth between the Flex client and the server, working with a CF socket server, and the Flex gateways. Fiddler and Ethereal are free, Charles has a 30 day trial, then is a $50 registration, as of this writing.
A screenshot of Charles in action is shown below. For getting an understanding of what is happening when, and for simulating network delays through throttling (these tools allow this), there is simply no substitution. The debugging tool in Flex Builder is pretty good, trace is my good friend. But a tool to watch the client to server communication is quite helpful. I don’t promote any one over any other.
Theoretically, it would be possible to put something like this together using Flex, and Zinc (for System access), or Apollo. The Socket class is there, and listening on a socket is one technical challenge that’s mostly ready. To act as a proxy (listen in between), it’d have to be able to swap out a port on IE (there’s an API call for that). The tricky part is what’s in the middle: Organizing the packets by source, destination, type, and breaking down the inner details so that they’re easily digestible.