IPhone – What port does Skype for iPhone 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:

<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"> 
<host>9.channel</host> 
<port>80</port> 
<channel>p_123456789</channel> 
<seq>0</seq> 

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?

You don't need to open any ports on your firewalls for push notifications to work on your iPhone.

My iOS devices spent 90% of the time behind firewalls that don't allow any inbound connections to them. Notifications work fine (even with mobile data turned off).

The Apple docs at http://support.apple.com/kb/HT3576 do talk about port 5223. But they will be referring to out going connections on that port (even though they don't explicitly state that). Your firewall is unlikely to be blocking those, though I guess it is worth checking. I guess it is also possible that your ISP is blocking the out going port, but again that seems unlikely.

Despite the "push" in its name, Push Notifications are actually more accurately "pull" notifications (like most things with "push" in their name). The iOS device connects to Apple on port 5223 to listen in for the notifications.