How to check internet access on Android? InetAddress never times out


I got a AsyncTask that is supposed to check the network access to a host name. But the doInBackground() is never timed out. Anyone have a clue?

public class HostAvailabilityTask extends AsyncTask<String, Void, Boolean> {

    private Main main;

    public HostAvailabilityTask(Main main) {
        this.main = main;

    protected Boolean doInBackground(String... params) {
        Main.Log("doInBackground() isHostAvailable():"+params[0]);

        try {
            return InetAddress.getByName(params[0]).isReachable(30); 
        } catch (UnknownHostException e) {
        } catch (IOException e) {
        return false;       

    protected void onPostExecute(Boolean... result) {

        if(result[0] == false) {

7/26/2016 3:13:52 PM

Accepted Answer

Network connection / Internet access

  • isConnectedOrConnecting() (used in most answers) checks for any network connection
  • To know whether any of those networks have internet access, use one of the following

A) Ping a Server (easy)

// ICMP 
public boolean isOnline() {
    Runtime runtime = Runtime.getRuntime();
    try {
        Process ipProcess = runtime.exec("/system/bin/ping -c 1");
        int     exitValue = ipProcess.waitFor();
        return (exitValue == 0);
    catch (IOException e)          { e.printStackTrace(); }
    catch (InterruptedException e) { e.printStackTrace(); }

    return false;

+ could run on main thread

- does not work on some old devices (Galays S3, etc.), it blocks a while if no internet is available.

B) Connect to a Socket on the Internet (advanced)

// TCP/HTTP/DNS (depending on the port, 53=DNS, 80=HTTP, etc.)
public boolean isOnline() {
    try {
        int timeoutMs = 1500;
        Socket sock = new Socket();
        SocketAddress sockaddr = new InetSocketAddress("", 53);

        sock.connect(sockaddr, timeoutMs);

        return true;
    } catch (IOException e) { return false; }

+ very fast (either way), works on all devices, very reliable

- can't run on the UI thread

This works very reliably, on every device, and is very fast. It needs to run in a separate task though (e.g. ScheduledExecutorService or AsyncTask).

Possible Questions

  • Is it really fast enough?

    Yes, very fast ;-)

  • Is there no reliable way to check internet, other than testing something on the internet?

    Not as far as I know, but let me know, and I will edit my answer.

  • What if the DNS is down?

    Google DNS (e.g. is the largest public DNS in the world. As of 2013 it served 130 billion requests a day. Let 's just say, your app would probably not be the talk of the day.

  • Which permissions are required?

    <uses-permission android:name="android.permission.INTERNET" />

    Just internet access - surprise ^^ (Btw have you ever thought about, how some of the methods suggested here could even have a remote glue about internet access, without this permission?)


Extra: One-shot AsyncTask Example

class InternetCheck extends AsyncTask<Void,Void,Boolean> {

    private Consumer mConsumer;
    public  interface Consumer { void accept(Boolean internet); }

    public  InternetCheck(Consumer consumer) { mConsumer = consumer; execute(); }

    @Override protected Boolean doInBackground(Void... voids) { try {
        Socket sock = new Socket();
        sock.connect(new InetSocketAddress("", 53), 1500);
        return true;
    } catch (IOException e) { return false; } }

    @Override protected void onPostExecute(Boolean internet) { mConsumer.accept(internet); }

// Usage

    new InternetCheck(internet -> { /* do something with boolean response */ });

Extra: One-shot RxJava/RxAndroid Example (Kotlin)

fun hasInternetConnection(): Single<Boolean> {
  return Single.fromCallable {
    try {
      // Connect to Google DNS to check for connection
      val timeoutMs = 1500
      val socket = Socket()
      val socketAddress = InetSocketAddress("", 53)

      socket.connect(socketAddress, timeoutMs)

    } catch (e: IOException) {

    // Usage

    hasInternetConnection().subscribe { hasInternet -> /* do something */}
6/20/2018 9:48:28 AM

If the device is in airplane mode (or presumably in other situations where there's no available network), cm.getActiveNetworkInfo() will be null, so you need to add a null check.

Modified (Eddie's solution) below:

public boolean isOnline() {
    ConnectivityManager cm =
        (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    return netInfo != null && netInfo.isConnectedOrConnecting();

Also add the following permission to the AndroidManifest.xml:

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

One other small point, if you absolutely need a network connection at the given point in time, then it might be better to use netInfo.isConnected() rather than netInfo.isConnectedOrConnecting. I guess this is up to the individual use-case however.

Licensed under: CC-BY-SA with attribution
Not affiliated with: Stack Overflow