HttpRespond always throws IOException

Question

I want to send Parameters to PHP page and wait for receive String Respond but it always throws IOException when i pass this

HttpResponse response = httpclient.execute(httppost);

it try to execute both android device and emulator this is my fuction

 public String HTTPPostData(String url,String... params) throws IllegalStateException, IOException {   
    // Create a new HttpClient and Post Header   
    HttpClient httpclient = new DefaultHttpClient();   
    HttpPost httppost = new HttpPost(url);   

   // Add your data   
    List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);   
    for (int i=0;i<params.length;i++){
        nameValuePairs.add(new BasicNameValuePair("params_" + i, params[i]));   
     }
    httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

    // Execute HTTP Post Request   
    HttpResponse response = httpclient.execute(httppost);
    InputStream is = response.getEntity().getContent();

     BufferedInputStream bis = new BufferedInputStream(is);
     ByteArrayBuffer baf = new ByteArrayBuffer(20);

     int current = 0;  

     while((current = bis.read()) != -1){  
      baf.append((byte)current);}

    return new String(baf.toByteArray());
}