How to disable internet access (local only) in tethering mode?

Question

I've created this tethering connection but I would prefer do not share any 3G/4G connection because I need it only for access to a local web server, how I can disable access to it?

    wifi   = (WifiManager) getSystemService(Context.WIFI_SERVICE);

    Method[] wmMethods  = wifi.getClass().getDeclaredMethods();

    for (Method method: wmMethods){
        if (method.getName().equals("setWifiApEnabled")){
            try {

                WifiConfiguration netConfig = new WifiConfiguration();
                netConfig.SSID = "WifiConnection";
                netConfig.allowedKeyManagement.set(WifiConfiguration.KeyMgmt.NONE); 

                method.invoke(wifi, netConfig, true);
            } catch (IllegalArgumentException e){
                e.printStackTrace();
            } catch (IllegalAccessException e){
                e.printStackTrace();
            } catch (InvocationTargetException e){
                e.printStackTrace();
            }
        }
    }   

}