How To Send Requests To A Server In JSON Format

I am trying to send requests to a server in JSON format but my app die on the emulator when i try to send request. However the same code works fine as a normal java application.

Here is my code:

Code:
private HttpResponse doRequest(String url,JSONObject jso){
HttpClient client = new DefaultHttpClient();
HttpPost request = new HttpPost(url);
HttpResponse response = null;

[Code]...

What wrong with this code if it run perfectly in a java application?