I am sending UDP packets to a remote, and I would like to know the IP of the local interface that will be used for that. In a shell I would run:
ip route get 192.168.1.54
and it would answer something like:
192.168.1.12 dev wlan0 table local_network src 192.168.1.1
Where I'm interested in getting the src: 192.168.1.1.
I can do it by calling exec like this:
Runtime.getRuntime().exec("ip route get 192.168.1.54")
but that does not seem very elegant and I don't know which devices support that (it works on some of them, and others return an error code "1" though the command works in adb shell).
Is there a way to do that with the Android SDK? I looked at the ConnectivityManager but could not find a way...
It looks like you want the address of the network's gateway for your WiFi network.
This function is based on doc and some examples.
public InetAddress getGateway(Context context) {
ConnectivityManager connectivityManager =
(ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
// getActiveNetwork() requires M or later.
return null;
}
Network activeNetwork = connectivityManager.getActiveNetwork();
if (activeNetwork == null) {
return null;
}
List<RouteInfo> routes = connectivityManager.getLinkProperties(activeNetwork).getRoutes();
for (RouteInfo route : routes) {
if (route.isDefaultRoute() && !(route.getGateway() instanceof Inet6Address)) {
return route.getGateway();
}
}
return null;
}