Android - Detect if Wifi Requires Browser Login

Question

My university has an open wifi access point, however it requires you to enter your e-mail before it allows you to use the web. My problem is that the Wifi is stupid in that

Answer 1

See the "Handling Network Sign-On" section of the HttpUrlConnection documentation:

Some Wi-Fi networks block Internet access until the user clicks through a sign-on page. Such sign-on pages are typically presented by using HTTP redirects. You can use getURL() to test if your connection has been unexpectedly redirected. This check is not valid until after the response headers have been received, which you can trigger by calling getHeaderFields() or getInputStream().

They have a snippet of sample code there. Whether this will cover your particular WiFi AP, I can't say, but it is worth a shot.

Answer 2

I used the following code using google's 204 endpoint.

 private boolean networkAvailable() {

        ConnectivityManager mManager = (ConnectivityManager) getApplicationContext().getSystemService(Context.CONNECTIVITY_SERVICE);
        if(mManager != null) {
            NetworkInfo activeNetwork = mManager.getActiveNetworkInfo();
            if(activeNetwork== null || !activeNetwork.isConnectedOrConnecting()){
                return false;
            }
        }

        OkHttpClient client = new OkHttpClient();

        Request request = new Request.Builder()
                .url("http://clients1.google.com/generate_204")
                .build();
        try {
            Response response = client.newCall(request).execute();
            if(response.code() != 204)
                return  false; // meaning it either responded with a captive html page or did a redirection to captive portal.
            return true;
        } catch (IOException e) {
            return true;
        }
    }

Many applications including Google Chrome use http://clients1.google.com/generate_204 to verify that the the connection is not locked under captive portal.

Answer 3

I think @FlyWheel is on the right path, but I would use http://clients1.google.com/generate_204 and if you don't get a 204, you know you are behind a captive portal. You can run this in a loop until you do get a 204 in which case you know you are not behind a captive portal anymore.

@FlyWheel wrote: The only downside is this would also indicate that a web login is required when there is simply no internet connectivity on the WiFi access point.

You can solve this by registering a receiver to android.net.conn.CONNECTIVITY_CHANGE. You can check if Wifi is ON and is connected by looking at the Supplicant State of the connection.

Here is a snippet, but I didn't run it:

WifiManager wm = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
WifiInfo wifiInfo = wm.getConnectionInfo();
SupplicantState suppState = wifiInfo.getSupplicantState();

if (wm.isWifiEnabled()) {
   if (suppState == SupplicantState.COMPLETED){
      // TODO - while loop checking generate_204 (FlyWheels code)Using intent service.
   }
}

I can't remember if the SupplicantState is COMPLETED or ASSOCIATED, you will have to check that. You should use an IntentService for checking the generate_204 since broadcast receivers have a short lifetime.

Answer 4

Ping an external IP address (like google.com) to see if it responds.

    try {
        Runtime runtime = Runtime.getRuntime();
        Process proc = runtime.exec("ping -c 1 " + "google.com");
        proc.waitFor();     
        int exitCode = proc.exitValue();
        if(exitCode == 0) {
            Log.d("Ping", "Ping successful!";
        } else {
            Log.d("Ping", "Ping unsuccessful.");
        }
    } 
    catch (IOException e) {}
    catch (InterruptedException e) {}

The only downside is this would also indicate that a web login is required when there is simply no internet connectivity on the WiFi access point.

@CommonsWare I believe this is a better answer than opening a UrlConnection and checking the host, since the host doesn't always change even when displaying the redirect page. For example, I tested on a Belkin router and it leaves whatever you typed in the browser as is, but still displays its own page. urlConnection.getUrl().getHost() returns what it should because of this.

Answer 5

The issue might rather be - today at least - that newer Android versions (5.1+?) keep the 3G/4G connection up and running until the wifi login actually leads to a fully functional wifi connection.

I haven't tried it, but maybe with the enum value CAPTIVE_PORTAL_CHECK of NetworkInfos DetailedState one can try to detect such a mode properly?