Get IP address of computer in tether mode

Question

Is there a programmatic way for an Android device to check the IP address of the computer to which it is connected to while the phone is in tether mode? Also, the WiFi and data have to be turned off.

Answer 1

If you're checking the public IP address of your computer, then you'll need to ask an outside server: https://stackoverflow.com/a/2939223/2201238

If you're looking for the local IP address of the computer with respect to the tethered network, you'll need to find the gateway IP of that network. It's possible to do this by finding the system property dhcp.interface_name_here.gateway. Where you'd replace interface_name_here with another value, like wlan0 (wifi), rmnet[012345] (cell or usb tethering), p2p (wifi direct), or if you're using HoRNDIS rndis0.

@Nullable
public String getTetheredGatewayIp() {
    NetworkInterface tetheredNic = getTetheredNetworkInterface();
    try {
        Class<?> systemPropertiesClass = Class.forName("android.os.SystemProperties");
        return (String) systemPropertiesClass
                .getMethod("get", String.class)
                .invoke(systemPropertiesClass, "dhcp." + tetheredNic.getName() + ".gateway");
    } catch (Exception ignore) {}
    return null;
}

// Find the NetworkInterface of any 'rndis' NIC:
@Nullable
private NetworkInterface getTetheredNetworkInterface() {
    Enumeration<NetworkInterface> networkInterfaces = NetworkInterface.getNetworkInterfaces();
    while (networkInterfaces.hasMoreElements()) {
        NetworkInterface nic = networkInterfaces.nextElement();
        if (nic.isUp() && !nic.isLoopback() && nic.getName().contains("rndis")) {
            return nic;
        }
    }
    return null;
}