UnknownHostException is thrown in android app if hostname is used instead of IP address

I have the following code which I use to send a request to the server.

String inputXML = createInputXML(searchText);
HttpClient httpclient = new DefaultHttpClient();
String url = "http://mysite.com/action";//Works fine if I use IP address directly,for eg:http://1.2.3.4/action
HttpPost httppost = new HttpPost(url);
HttpResponse response=null;
StringEntity se = null;
try {
    se = new StringEntity(inputXML, HTTP.UTF_8);
} catch (UnsupportedEncodingException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
se.setContentType("text/xml");  
httppost.setHeader("Content-Type","application/xml;charset=UTF-8");
httppost.setEntity(se);  
try {
    response = httpclient.execute(httppost);
} catch (ClientProtocolException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

When I run the program on emulator I am getting a UnKnownHostException on the line

response = httpclient.execute(httppost);

If I use the ip address directly instead of host name,the request is sent correctly. Please note the following points:

1. I am using Android 2.3.3
2. I have added <uses-permission android:name="android.perm开发者_运维百科ission.INTERNET"></uses-permission> in the manifest xml
3. Proxy settings are updated in the emulator's APN.
4. Using the browser in the emulator I can access a website with their host names.

Any idea why this is causing an issue?

Please make sure, you followed all steps 1-4 user700284 described in his Question.

HttpClient client = new DefaultHttpClient();


//Get the default settings from APN (could be also hard coded stuff)
  String proxyHost = android.net.Proxy.getDefaultHost();
  int proxyPort = android.net.Proxy.getDefaultPort();
//Set Proxy params of client, if they are not the standard
    if (proxyHost != null && proxyPort > 0) {
        HttpHost proxy = new HttpHost(proxyHost, proxyPort);
        client.getParams().setParameter(ConnRoutePNames.DEFAULT_PROXY, proxy);
    }
HttpGet request = new HttpGet("http://www.google.com");

The url has nothing to do with the line

se = new StringEntity(inputXML, HTTP.UTF_8);

are you sure it is this line?