Flash :: Comet-style Long-Poll In AIR Using URLStream

I'm attempting to connect to an existing Comet-style long-poll service using an AIR app. The service expects a client to make a GET request with a Connection: Keep-Alive header. This request will remain open for long periods of time so that the server can push data through. In my app, the connection is terminated with an IOError after 30 seconds.

Is this an undocumented limitation of URLStream? A restriction on adl (I've only been running my app through adl)?

The server does not send any "keep-alive" messages to the client but, unfortunately this is not something i have control over.

Update

To test this, I've set up a stripped-down version using a little php script (linked by leggetter below) and am hitting it from a simple AIR app. I'm finding that my connections are closed after 30 seconds whether I use URLStream or URLLoader. the PHP:

<?php
set_time_limit(0);
sleep(40);

[Code]....

If i adjust the initial sleep time in the php script to anything over 30 seconds, the IOError event is triggered. If I lower the sleep time, but the request continues adding data past 30 seconds, the onComplete event is called, but _urlLoader.data is empty.

The only way this process completely successfully is if the entire thing is over before 30 seconds elapses.