Unable to get stack trace of `java.net.UnknownHostException` in android

Question

I'm trying to get ip address of machine with host name nirranjan-pc in android and tried using below code as per the answer of this question

Log.e(tag, "In background method :: ");
try {
    String ip = InetAddress.getByName("nirranjan-pc").getHostAddress();
    Log.e(tag, "++++++++++++ IP FOUND :: " + ip);
} catch (Exception ex) {
    Log.e(tag, "Exception:: " + ex);
    Log.e(tag, Log.getStackTraceString(ex));
    Log.e(tag, "Exception Host ", ex);
} finally {
    Log.e(tag, "Finally::");
}

but i was not getting the ip address and unable to get full stack trace of UnknownHostException using Log.e(tag, Log.getStackTraceString(ex)); and Log.e(tag, "Exception Host ", ex); methods.

Only Log.e(tag, "Exception:: " + ex); method works fine.

my logcat is below.

02-23 12:23:24.308 16507-16618/in.gauriinfotech.sevadeal E/Favour: In background method :: 
02-23 12:23:24.350 16507-16513/in.gauriinfotech.sevadeal W/art: Suspending all threads took: 14.457ms
02-23 12:23:24.377 16507-16618/in.gauriinfotech.sevadeal E/Favour: Exception:: java.net.UnknownHostException: Unable to resolve host "nirranjan-pc": No address associated with hostname
02-23 12:23:24.380 16507-16618/in.gauriinfotech.sevadeal E/Favour: Exception Host 
02-23 12:23:24.380 16507-16618/in.gauriinfotech.sevadeal E/Favour: Finally::

My Question

1) Why Log.e(tag, Log.getStackTraceString(ex)); and Log.e(tag, "Exception Host ", ex); methods not functioning properly and no giving stack trace.

2) I'm getting correct IP address without any error in java desktop application. Why it is not working in android?

-- Also i tried to access same using Google Chrome browser in android

It works fine with IP address

But not working with Machine Name

AND strange is that, when i try to open website from browser from Windows Phone, it opens with no error.

Answer 1

The reason of your stacktrace is in the source of the Log class.
The UnknownHostException exceptions are not printed .

If you check the code you can see that Log.getStackTraceString() method has been patched in ICS to return in empty String in case of UnknownHostException .

Here the relevant code :

//To reduce the amount of log spew that apps do in the non-error
// condition of the network being unavailable.

Throwable t = tr;
while (t != null) {
    if (t instanceof UnknownHostException) {
        return "";
    }
 t = t.getCause();

Answer 2

Regarding your first question, try Throwable.printStackTrace(PrintWriter pw) to get the stack trace like:

StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw);
ex.printStackTrace(pw);
Log.e(tag, sw.toString());

For your second question it is probably your DNS is not configured correctly to lookup and translate a hostname to a correct IP.

EDIT:

Take a look at this for your second question as well Android Browser hostnames does not get resolved if domain name is not appended