Android and Ios: Simultaneous Wifi to local host and LTE for internet on mobile devices.

We have a small service hosted on intranet (without any internet gateway) that users access through wifi. The service is based on MVC. When users turn on wifi and connect to local network, they lose data connectivity provided by their phones. Project needs a solution whereby : 1. The MVC browser is packaged as an app for android and ios both. [login to view URL] proposed solution requires some special developer access etc., a record of original settings shoudl be kept and setting restored on uninstalling the app. 3. Once app is launched, device to connect automatically to our standard SSD-id. All local host traffic to go to the local host and all internet traffic to be routed to the internet over users data connection. The solution should be backward compatible to work on all IoS versions active for last 3 years.