I uploaded my app on itunes multiple times and received the following message:
( We discovered one or more bugs in your app when reviewed on iPhone running iOS 10.2 on Wi-Fi connected to an IPv6 network.
Specifically, when we attempted to create a new account a loading indicator spun indefinitely. )
Apps are reviewed on an IPv6 network. Please ensure that your app supports IPv6 networks, as IPv6 compatibility is required.
Notes: I have used AFNetworking version 3.1.0 for call web services(support IPV6) and Apple Reachability(also support IPV6) without using hard coded Ip.
My question: the changes must be done on mobile side or server side?
As far as my experience with IPv6 reaches, you're probably right. When you develop your app in Xcode using the latest SDK for iOS 10.2, you should be save with IPv6 compatibility on your app's side.
However, Unix (MacOS audios are a Unix derivative) takes the path or url from your app and will negotiate at the OS level with the other side you want to connect with. This usually runs over a DNS. So, your app and iOS will first request an IPv6 IP address from the DNS. When the DNS understands IPv6, which is not always guaranteed, but it usually does, it asks the other side for an IPv6 address. If the other side does not support IPv6, the operating system will request an IPv4 address and set up the connection.
Since Apple will hold you responsible for the entire chain of services delivered by your app, you must ensure the requested side also supports IPv6 via it is part of the your apps functionality.
Hope this helps.