Question

I’m writing an android application which should send out broadcast packets over WiFi.

Currently I can get the IP address of the device from WifiManager.getConnectionInfo().getIpAddress() and guess the broadcast address by simply replacing the last digit with 0. But I really don’t like this solution.

What would be the proper way?

Answer 1

You need to replace with 255 not with 0.

If you are targeting SDK 9 or later you can use getBroadcast(), otherwise you need to overide the numbers in IP address.

Example code:

public static InetAddress getNetworkLocalBroadcastAddressdAsInetAddress() throws IOException {
    for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) {
        NetworkInterface intf = en.nextElement();
        if(VERSION.SDK_INT < 9) { 
            if(!intf.getInetAddresses().nextElement().isLoopbackAddress()){
                byte[] quads = intf.getInetAddresses().nextElement().getAddress();
                quads[0] = (byte)255;
                quads[1] = (byte)255;
                return InetAddress.getByAddress(quads);
            }
        }else{
            if(!intf.isLoopback()){
                List<InterfaceAddress> intfaddrs = intf.getInterfaceAddresses();
                return intfaddrs.get(0).getBroadcast(); //return first IP address
            }
        }
    }
    return null;
}