If I understand it correctly, Push Notifications are sent to port # 5223. Now, which server port we are talking about here. I am running my application on a device which is on some WiFi network.
I want to know the host name (IP address) of the server on whose port # 5223 Pushes are sent by APNS.
Apple answers your question very clearly here
The APNs servers use load balancing. Your devices will not always connect to the same public IP address for notifications. The entire 126.96.36.199/8 address block is assigned to Apple, so it's best to allow this range in your firewall settings.
And to clarify the ports thingy, the devices use port 5223 to communicate to the APNs servers or port 443 as a fallback on Wi-fi only, when devices are unable to communicate to APNs on port 5223.