Using Cellular Network for Phone Number Verification even when Wifi is on

Using WiFi is more complicated when trying to use IPification Authentication. By default, all traffic on all operating systems will favor WiFi above cellular connections. However for IPification, the API request must be made using the cellular connection. We realize that users are unlikely to turn off WiFi and so the following code is provided for both iOS and Android to include in your applications that will allow a small payload to be delivered over the cellular interface, even when WiFi is connected. Telcos usually don’t charge (zero rate) our Authentication URLs so end users won’t have any cost.

Android

The following will allow Android applications using Android API 21+ to use Cellular for the API request.

Minimum Android

Android 5.0 (API 21) and up

Permission

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />

Network 3rd Library

OKHttp3 version 3 / 4.
We use OKHttp3 because it supports socket and target DNS

implementation 'com.squareup.okhttp3:okhttp:4.9.0'

Core Function

Here's a function that can simplify the action of preferring certain types of networks for your application

val builder: NetworkRequest.Builder = NetworkRequest.Builder()
builder.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
builder.addTransportType(NetworkCapabilities.TRANSPORT_CELLULAR);

After this you are able to get onAvailable() callback from system and later you set process default network as mobile data.

val mNetworkCallBack = object: ConnectivityManager.NetworkCallback() {
    override fun onAvailable(network: Network) {
        super.onAvailable(network)
    }
    override fun onUnavailable() {
        super.onUnavailable()
    }
    override fun onLost(network: Network) {
        super.onLost(network)
    }
}

val manager = mContext.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
manager.requestNetwork( builder.build(), mNetworkCallBack)

More Detail here: Android_CellularConnection.kt

iOS

For iOS 12 and newer, we use NetWork framework to make network connection via cellular interface.

For iOS under 12, we use CocoaAsyncSocket (7.6.4). Because iOS under 12 doesn’t support an official API to force connection to cellular interface, we need to do it manually by using a socket library to force requests to use cellular. Then find the cellular interface from getifaddrs, pass that interface to the socket function, socket bind will happen with cellular.

Core Function

Using the following would be the correct approach to force the connection over cellular:

let tcpOptions = NWProtocolTCP.Options()
let params = NWParameters(tls: enableTLS ? options : nil, tcp: tcpOptions)
params.requiredInterfaceType = .cellular
self.connection =  NWConnection.init(host:  host  , port: port, using: params)

After the connection moves into the .ready state and the connection is setup on pdp_ip0 (cell)

connection.stateUpdateHandler = { (newState) in
    print("TCP state change to: \(newState)")
    switch newState {
    case .ready:
        print("ready")
        // self.delegate!.didConnect(socket: self)
        break
    case .waiting(let error):
        print("waiting error \(error.debugDescription ?? "")")
        break

    case .failed(let error):
        print("failed \(error.debugDescription ?? "")")
        // self.delegate?.didDisconnect(socket: self, error: error)
        break
    case .cancelled:
        print("cancelled" )
        break
    default:
        print("default")
        break
    }
}
connection.start(queue: .main)

More Detail here: iOS_CellularConnection.swift

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