What port does iPhone native Facebook app use?
First, this is a really good question. Wow. I've been trying for days to figure out how to attack this one.

I set up "Charles Web Debugging Proxy" on my Mac and set up my iPhone to hit it.

First, it hits http://api.facebook.com/restserver.php, which spits this back:

&lt;chat_connect_response xmlns="http://api.facebook.com/1.0/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://api.facebook.com/1.0/ http://api.facebook.com/1.0/facebook.xsd"&gt; 
&lt;host&gt;9.channel&lt;/host&gt; 
&lt;port&gt;80&lt;/port&gt; 
&lt;channel&gt;p_123456789&lt;/channel&gt; 
&lt;seq&gt;0&lt;/seq&gt; 




Meanwhile, it also connects to iphone.facebook.com which gives some XML. Then it connects to 0.9_channel.facebook.com:80 and sends some requests which return JSON.

It looks like everything is done over port 80. Are you sure theres no other problem on your end?