Android app fails to get access to the network

问题

I am trying to connect to a chat server on the internet from an Android app so first I test whether I have contact with the server from an AsyncTask:

@Override
    protected Void doInBackground(SocketAndEditText... soEd) {
    try{
            InetAddress address1 = InetAddress.getByName("130.237.161.23");
            boolean reachable = address1.isReachable(4456);
            //...
    } catch (Exception e) {
        //...
    }
}

When I run the above code the variable reachable gets the value false but when I run the same code as a simple Java console application I get true:

import java.net.InetAddress;
public class Test {
    public static void main(String[] args) {
        try{
            InetAddress address1 = InetAddress.getByName("130.237.161.23");
            boolean reachable = address1.isReachable(4456);
            System.out.println(reachable);
        } catch (Exception e) {
            //...
        }
    }
}

In my manifest file I have <uses-permission android:name="android.permission.INTERNET" />

Why does it not work in Android but works as a Java application?

来源：https://stackoverflow.com/questions/10575747/android-app-fails-to-get-access-to-the-network