android - Check real internet connection

Question

In my application I need to check whether device is connected to Internet. I tried using ConnectivityManager but it doesn't give a 100% precise result. For instance, I might have a wi-fi connection but still don't have access to internet resources. In my case I've got to open a VPN connection, after I've connected to via wi-fi, in order to get real access to Internet. So the approach with ConnectivityManager doesn't work.

So, regarding the above - should I write a manual http request in order to ensure or there's another way ?

Here's some code I'm using

ConnectivityManager cm =  (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        return cm.getActiveNetworkInfo() != null && cm.getActiveNetworkInfo().isConnected() && cm.getActiveNetworkInfo().isAvailable();

Answer 1

Yes, you are correct, to check that you can reach the internet you need to test that explicitly. If you need HTTP access you can try connecting to the host you later on want to connect to.

You should however use the connection method that you intend to use later on. HTTP can work but not FTP. So if you need FTP access you should test it.

---

If you also want to get the external IP you can use this method:

public static InetAddress getExternalIp() throws IOException {
    URL url = new URL("http://automation.whatismyip.com/n09230945.asp");
    URLConnection connection = url.openConnection();
    connection.addRequestProperty("Protocol", "Http/1.1");
    connection.addRequestProperty("Connection", "keep-alive");
    connection.addRequestProperty("Keep-Alive", "1000");
    connection.addRequestProperty("User-Agent", "Web-Agent");

    Scanner s = new Scanner(connection.getInputStream());
    try {
        return InetAddress.getByName(s.nextLine());
    } finally {
        s.close();
    }
}

If you successfully got an IP address back from this method, you can connect via HTTP to that.