I have a customer who has a device that has its own builtin wifi hot spot and he would like to connect it to an iPad 4G vie wifi and forward data at the same time through the cellular connection. Is this supported in IOS and if so can you point me to the appropriate documentation. Any suggestions are appreciated.
Jim
Comparing to Android, iOS supports simultaneous work of multiple network adapters. It's necessary to write C code working with BSD sockets, doing enum, bind, and handling network interface changes.
By the way, it's ideologically very important to continue using that native BSD functionality in C/C++, otherwise, who knows, Apple may in 5-10 years remove support for BSD sockets completely :-)
Some C examples of how to do that you can find here: https://gist.github.com/avesus/fdb465b60a4f5204845c
I've been looking for this answer myself and eventually found a solution here:
The solution does not involve any code but instead changing the settings on your iPad. Change the settings for the Wi-Fi connection to Static instead of DHCP. In the Static settings leave the Router field EMPTY. What I did was write down the IP Address, Subnet Mask, and DNS values that were being used by DHCP and then just left the Router field blank. I have found a couple of other posts that suggest entering 0 or 0.0.0.0 but leaving it blank was what made it work for me.
来源：https://stackoverflow.com/questions/18755051/does-ios-support-simultaneous-wifi-and-3g-4g-connections