Question

I’m trying to connect a socket to an non-existent server, and I really don’t understand why an exception is not being raised.

Here is my code:

public class TestSocket extends Activity {
    private static final String TAG = "TestSocket";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        BasicThread t = new BasicThread();
        t.start();
    }

    class BasicThread extends Thread {
        @Override
        public void run() {
            Log.d(TAG, "Before");
            try {
                new Socket("42.42.42.42", 12345);
                Log.d(TAG, "Connected");
            } catch (Exception e) {
                Log.d(TAG, "Exception");
            }
            Log.d(TAG, "After");
        }
    }
}

I also tried with my own IP address while running Wireshark, and I first get [SYN] from Android to my computer and then [RST, ACK] from my computer to Android (because nothing is listening at this port), but I still do not get an exception on Android.

Also I’m testing on a physical phone (Nexus S), and I do have the internet permission in my Manifest.

Why aren’t I getting an Exception?

Edit:

More precisely, the output I get is

D/TestSocket(17745): Before
D/TestSocket(17745): Connected
D/TestSocket(17745): After

(and not Exception)

Answer 1

In the Socket constructor, it’s thrown when the IP address of the host can’t be determined, so I assume that because you aren’t passing a hostname which needs resolution, a different exception would be getting thrown instead. I believe the exception actually comes from the URL class or such which does the resolution, and from nowhere else.

The connect(..) method should throw an exception but doesn’t appear to, as you say.

Edit: apparently Android (some versions) doesn’t work properly here, so it’s probably a bug: http://code.google.com/p/android/issues/detail?id=6144. It doesn’t look like the link refers to the emulator as I had thought.