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 8.8.8.8");
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("8.8.8.8", 53);
sock.connect(sockaddr, timeoutMs);
sock.close();
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. 8.8.8.8) is the largest public DNS in the world. As of 2018 it handled over a trillion queries a day [1]. 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 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("8.8.8.8", 53)
socket.connect(socketAddress, timeoutMs)
socket.close()
true
} catch (e: IOException) {
false
}
}
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
}
///////////////////////////////////////////////////////////////////////////////////
// Usage
hasInternetConnection().subscribe { hasInternet -> /* do something */}
Extra: One-shot RxJava/RxAndroid Example (Java)
public static Single<Boolean> hasInternetConnection() {
return Single.fromCallable(() -> {
try {
// Connect to Google DNS to check for connection
int timeoutMs = 1500;
Socket socket = new Socket();
InetSocketAddress socketAddress = new InetSocketAddress("8.8.8.8", 53);
socket.connect(socketAddress, timeoutMs);
socket.close();
return true;
} catch (IOException e) {
return false;
}
}).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread());
}
///////////////////////////////////////////////////////////////////////////////////
// Usage
hasInternetConnection().subscribe((hasInternet) -> {
if(hasInternet) {
}else {
}
});
Extra: One-shot AsyncTask Example
Caution: This shows another example of how to do the request. However, since AsyncTask is deprecated, it should be replaced by your App's thread scheduling, Kotlin Coroutines, Rx, ...
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("8.8.8.8", 53), 1500);
sock.close();
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 */ });
if(Runtime.getRuntime().exec("/system/bin/ping -c 1 8.8.8.8").waitFor()==0) .... See my answer for a nicer implementation of this. Btw the accepted answer (and many others here) just check for a network connection, not the internet. – Levite