If you have some documentation what exactly needs to be done, it might be good idea to share relevant parts, because currently we don't know any details.
But if it's some server in LAN and you want your iPhones to connect to it from internet, you'll probably need to forward required ports unconditionally for everyone. Because if iPhones can have any random address, depending on where they are connected, you can't easily recognize their connections from others.
Other approach would be using VPN to connect to router and through it to server, that would be secure. But I have no idea if it's something that iPhones can do.
People who quote full posts should be spanked with ethernet cable. Some exceptions for multi-topic threads may apply.