Upload multiple files from async http android but the success callback never gets received

Here is the code which help You.

public class uploadFiles extends AsyncTask<Void, Void, String> {
        private final ProgressDialog dialog = new ProgressDialog(
                PtoPPostActivity.this);
        protected void onPreExecute() {
            this.dialog.setMessage("Loading...");
            this.dialog.setCancelable(false);
            this.dialog.show();
        }
        @Override
        protected String doInBackground(Void... params) {
           String result=uploadFile(""); // inside the method paste your file uploading code
            return result;
        }
        protected void onPostExecute(String result) {
            // Here if you wish to do future process for ex. move to another activity do here
            if (dialog.isShowing()) {
                dialog.dismiss();
            }
            showDialog(PtoPPostActivity.this,result);
        }
    }

public String uploadFile(String req) {
        // TODO Auto-generated method stub

        String serverResponseMessage = "";
        String response_return = "";
        Log.d("first str is:", req);

        URL imageUrl = null;
        try {
            imageUrl = new URL(Constant.WEBSERVICE_URL); // get WebService_URL
        } catch (MalformedURLException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }

        String lineEnd = "\r\n";
        String twoHyphens = "--";
        String boundary = "---------------------------14737809831466499882746641449";
        // generating byte[] boundary here

        HttpURLConnection conn = null;
        DataOutputStream outputStream = null;

        int bytesRead, bytesAvailable, bufferSize;
        byte[] buffer;
        int maxBufferSize = 1 * 1024 * 1024;

        try {
            int serverResponseCode;
            conn = (HttpURLConnection) imageUrl.openConnection();
            conn.setConnectTimeout(30000);
            conn.setReadTimeout(30000);
            conn.setDoOutput(true);
            conn.setDoInput(true);
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);

            // json String request
            outputStream = new DataOutputStream(conn.getOutputStream());

            outputStream.writeBytes(twoHyphens + boundary + lineEnd);
            outputStream.writeBytes("Content-Disposition: form-data; name=\"json\"" + lineEnd);
            outputStream.writeBytes("Content-Type: text/plain;charset=UTF-8" + lineEnd);
            outputStream.writeBytes("Content-Length: " + req.length() + lineEnd);
            outputStream.writeBytes(lineEnd);
            outputStream.writeBytes(req + lineEnd);
            outputStream.writeBytes(twoHyphens + boundary + lineEnd);

            // image
            Log.i("images path==>", "" + imageArry); // get photo
            // local path

            for (int i = 0; i < imageArry.size(); i++) {
                try {
                    String filePath = imageArry.get(i).get("uploadedPath");
                    Log.d("filePath==>", imageArry.get(i).get("uploadedPath") + "");

                    //////////////////////////////////////////////////
                    //  Bitmap original = BitmapFactory.decodeFile(mFileTemp.getPath());
                    Bitmap original = BitmapFactory.decodeFile(filePath);
                    if (original != null) {
                        Bitmap newBitmap = original;

                        ByteArrayOutputStream stream = new ByteArrayOutputStream();
                        newBitmap.compress(Bitmap.CompressFormat.JPEG, 100, stream);
                        byte[] bitmapdata = stream.toByteArray();

                        File cacheDir = PtoPPostActivity.this.getCacheDir();
                        File f = new File(cacheDir, "temp" + i + ".jpeg");
                        //write the bytes in file
                        FileOutputStream fos = new FileOutputStream(f);
                        fos.write(bitmapdata);
                        FileInputStream fileInputStream = new FileInputStream(f);
                        String lastOne = "temp";
                        /////////////////////////////////////////////

                        outputStream.writeBytes(twoHyphens + boundary + lineEnd);

                        outputStream.writeBytes("Content-Disposition: attachment;  name=\"imagePath" + i + "\"; filename=" + lastOne + i + ".jpeg" + lineEnd); // pass key & value of photo

                        outputStream.writeBytes("Content-Type: application/octet-stream" + lineEnd);
                        outputStream.writeBytes(lineEnd);

                        bytesAvailable = fileInputStream.available(); // photo size bytes
                        bufferSize = Math.min(bytesAvailable, maxBufferSize);
                        buffer = new byte[bufferSize];

                        // Read file
                        bytesRead = fileInputStream.read(buffer, 0, bufferSize);

                        while (bytesRead > 0) {
                            outputStream.write(buffer, 0, bufferSize);

                            bytesAvailable = fileInputStream.available();
                            bufferSize = Math.min(bytesAvailable, maxBufferSize);
                            bytesRead = fileInputStream.read(buffer, 0, bufferSize);
                        }

                        outputStream.writeBytes(lineEnd);

                        Log.d("posttemplate", "connection outputstream size is " + outputStream.size());
                        fileInputStream.close();
                    }
                } catch (OutOfMemoryError o) {
                    continue;
                }
            }

            outputStream.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);

            serverResponseCode = conn.getResponseCode();
            serverResponseMessage = conn.getResponseMessage();

            InputStream is = conn.getInputStream();
            BufferedReader rd = new BufferedReader(new InputStreamReader(is));
            String line;
            StringBuffer response1 = new StringBuffer();
            while ((line = rd.readLine()) != null) {
                response1.append(line);
                response1.append('\r');
            }

            rd.close();
            response_return = response1.toString();

            Log.d("posttemplate", "server response code " + serverResponseCode);
            Log.d("posttemplate", "server response message "
                    + serverResponseMessage);
            outputStream.flush();
            outputStream.close();
            conn.disconnect();

        } catch (MalformedURLException e) {
            Log.d("posttemplate", "malformed url", e);
            // Toast.makeText(getApplicationContext(),e.toString(),
            // Toast.LENGTH_LONG).show();
            // TODO: catch exception;
        } catch (IOException e) {
            Log.d("posttemplate", "ioexception", e);
            // Toast.makeText(getApplicationContext(),e.toString(),
            // Toast.LENGTH_LONG).show();
            // TODO: catch exception
        }
        Log.d("response--->", "****" + response_return);
        global_response = response_return;
        return response_return;
    }