After we submit our iOS application to AppReview team, they rejected our application and wrote :

We discovered one or more bugs in your app when reviewed on iPad running iOS 11.2.6 on Wi-Fi connected to an IPv6 network.

In order to solve the problem, we started to enable ipv6 on our servers.

This is how we did:

1) First of all, enable ipv6 network on your digitalocean droplet panel.

More info: https://www.digitalocean.com/community/tutorials/how-to-enable-ipv6-for-digitalocean-droplets

After that, you must enable ipv6 network on your droplet itself.

sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0
IPV6INIT=yes
IPV6ADDR=YOUR_IPv6_ADDRESS/64
IPV6_DEFAULTGW=YOUR_IPv6_GATEWAY
IPV6_AUTOCONF=no
DNS1=YOUR_IPv6_DNS_SERVER1
DNS2=YOUR_IPv6_DNS_SERVER2
DNS3=YOUR_IPv6_DNS_SERVER3

 

2) After this configuration, reboot the machine and check if your machine can ping ipv6 of google.com;

ping6 2001:4860:4860::8888

if you receive packages, it means you have enabled ipv6 network on your server.

 

3) After this point, you must add AAAA record for your domain in order to be reachable from ipv6 requests.

[blabla.com.] [AAAA] => YOUR_IPv6_ADDRESS

 

4) Now, you must listen ipv6 connection requests on nginx too, check if you built nginx with ipv6 support or not by typing: 

nginx -V

If you see –with-ipv6 then it is ready for ipv6 connections.

Open your domain nginx configuration, below the listen 80; line add listen [::]:80; and then restart the nginx.

Congratulations, you are ready for ipv6 connections now.

Don’t forget to test it on : http://ipv6-test.com/validate.php

If you see AAAA recordIPv6 web server and IPv6 DNS server are all OK, then it means everything works fine.