How do you check if you can connect to the internet via java? One way would be:
final URL url = new URL("http://www.google.com");
final URLConnection conn = url.openConnection();
... if we got here, we should have net ...
But is there something more appropriate to perform that task, especially if you need to do consecutive checks very often and a loss of internet connection is highly probable?
You can simply write like this
import java.net.InetAddress;
import java.net.UnknownHostException;
public class Main {
private static final String HOST = "localhost";
public static void main(String[] args) throws UnknownHostException {
boolean isConnected = !HOST.equals(InetAddress.getLocalHost().getHostAddress().toString());
if (isConnected) System.out.println("Connected");
else System.out.println("Not connected");
}
}
There are (nowadays) APIs for this, but they are platform specific:
On Android ConnectivityManager (https://developer.android.com/training/basics/network-ops/reading-network-state) does everything you need.
On Windows INetworkListManager::GetConnectivity (for which you'll need a JNI)
On generic Linux, you are probably stuck with testing if you have access to a DNS server and Google, as above.
there is probably an Apple way to do this as well
(I'd use the specific tools where available)
This have worked well for me.
try{
InetAddress addr = InetAddress.getByName("google.com" );
}catch(IOException e){
JOptionPane.showMessageDialog(new JFrame(),"No Internet connection.\nTry again later", "Network Error", JOptionPane.ERROR_MESSAGE);
}
The following piece of code allows us to get the status of the network on our Android device
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView mtv=findViewById(R.id.textv);
ConnectivityManager connectivityManager=
(ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if(((Network)connectivityManager.getActiveNetwork())!=null)
mtv.setText("true");
else
mtv.setText("fasle");
}
}
}