User Profile

I'm working on an iPhone-only app that connects to an external Wi-Fi accessory that's similar to a GoPro. When connected to the accessory's Wi-Fi network, the app is communicating with the accessory over a TCP connection, but the accessory does not have its own internet connection / should not share it with its clients. How can I configure this accessory so that iOS immediately recognizes that it has no internet connection and continues using cellular, showing the exclamation point over the current Wi-Fi in Settings?