How to check Internet access at realtime?

I found a lot of topics how to check the Internet access. But I cannot understand how to make it dynamically. For example, I send a request (it will work in a some another thread) and device loses the Internet connection. How I can cancel my request on this event?

Here's something I cooked earlier; maybe it will help:

    public class NetworkStateMonitor extends BroadcastReceiver {
        Context mContext;
        boolean mIsUp;

        public interface Listener {
            void onNetworkStateChange(boolean up);
        }

        public NetworkStateMonitor(Context context) {
            mContext = context;
            //mListener = (Listener)context;
            IntentFilter intentFilter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
            context.registerReceiver(this, intentFilter);
            mIsUp = isUp();
        }

        /**
        * call this when finished with it, and no later than onStop(): callback will crash if app has been destroyed
        */
        public void unregister() {  
            mContext.unregisterReceiver(this);
        }

        /*
        * can be called at any time
        */
        public boolean isUp() {
            ConnectivityManager connectivityManager = (ConnectivityManager) mContext.getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
            return activeNetworkInfo!=null && activeNetworkInfo.isConnectedOrConnecting();
        }

        /**
        * registerReceiver callback, passed to mListener
        */
        @Override public void onReceive(Context context, Intent intent) {       
            boolean upNow = isUp();
            if (upNow == mIsUp) return;     // no change
            mIsUp = upNow;
            ((Listener)mContext).onNetworkStateChange(mIsUp);
        }
    }