Switch between cellular and WiFi programmatically?

Question

How does the Speedify app switch between cellular and WiFi programmatically within the app?

With the Speedify app on, I "prioritized Cellular", ran a speed test, which showed the WiFi symbol on the whole time.

Then checked my cellular usage, and sure enough 111 MB was used even though wifi was never off.

I have read through NEVPNManager docs, which is used in the app, but can't seem to find anything. Perhaps SCNetworkConfiguration is used?

user_831785 · Answer

A possible solution is to use a static IP but don't put in any router IP as described here https://discussions.apple.com/thread/6448960 I think this can be achieved in code using Apple NetService framework