Connected to Internet or not connected? what is wrong with this code?

Question

hi
here is a simple code to check whether Internet is connected to my machine or not----------
import java.net.*;
class CheckNet
     public static void main(String args[])
          while(true)
               check();
               try{
               Thread.sleep(1000);
               }catch(InterruptedException ie){System.out.println(ie);}
     static void check()
          try
                         String hostAddress ;
                         InetAddress localHost ;
                              localHost = InetAddress.getLocalHost();
                              hostAddress = localHost.getHostAddress();
                              if (hostAddress.equals( "127.0.0.1" ))
                              System.out.println("Not connected");
                              else
                              System.out.println("Connect to host: " + hostAddress);
                    catch(UnknownHostException ukhe){System.out.println(ukhe);}
this code tells the status of connection at first call of method check() in code, but can not update itself i.e if status of net conn is changed prog continues to output the same result.
CAN ANYBODY HELP ME TO REMOVE THE BUG / or suggest a better way?
regards

Answer 1

I've run into the same issue and found the following:
InetAddress caches successful and unsuccessful host name resolutions (See JavaDocs for InetAddress for more detail on this).
My guess is that InetAddress has cached the unsuccessful attempt and therefore when a network connection is established in your application loop, InetAddress "thinks" its still not connected.
The JavaDocs say something about setting a security property which can control the cache time, but I haven't been able to get InetAddress to recognize the property change. I'm probably not setting it in the right place.
HTH,
robert