Question

I need to tell if my device has Internet connection or not. I found many answers like:

private boolean isNetworkAvailable() {
    ConnectivityManager connectivityManager 
         = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
    return activeNetworkInfo != null;
}

^{(Taken from Detect whether there is an Internet connection available on Android.)}

But this is not right, for example if I’m connected to a wireless network which doesn’t have Internet access, this method will return true… Is there a way to tell if the device has Internet connection and not if it is only connected to something?

Answer 1

You are right. The code you’ve provided only checks if there is a network connection.
The best way to check if there is an active Internet connection is to try and connect
to a known server via http.

public static boolean hasActiveInternetConnection(Context context) {
    if (isNetworkAvailable(context)) {
        try {
            HttpURLConnection urlc = (HttpURLConnection) (new URL("http://www.google.com").openConnection());
            urlc.setRequestProperty("User-Agent", "Test");
            urlc.setRequestProperty("Connection", "close");
            urlc.setConnectTimeout(1500); 
            urlc.connect();
            return (urlc.getResponseCode() == 200);
        } catch (IOException e) {
            Log.e(LOG_TAG, "Error checking internet connection", e);
        }
    } else {
        Log.d(LOG_TAG, "No network available!");
    }
    return false;
}

Of course you can substitute the http://www.google.com URL for any other server you want to connect to, or a server you know has a good uptime.

As Tony Cho also pointed out in this comment below, make sure you don’t run this code on the main thread, otherwise you’ll get a NetworkOnMainThread exception (in Android 3.0 or later). Use an AsyncTask or Runnable instead.

If you want to use google.com you should look at Jeshurun’s modification. In his answer he modified my code and made it a bit more efficient. If you connect to

HttpURLConnection urlc = (HttpURLConnection) 
            (new URL("http://clients3.google.com/generate_204")
            .openConnection());

and then check the responsecode for 204

return (urlc.getResponseCode() == 204 && urlc.getContentLength() == 0);

then you don’t have to fetch the entire google home page first.