public class LoginClass {
    public static class ValidarSesion extends AsyncTask<String,String,JSONObject>
    {
        @Override
        protected JSONObject doInBackground(String... parametros) {

            String datos = parametros[0];


            String JsonResponse = "";
            HttpURLConnection urlConnection = null;
            BufferedReader reader = null;
            OutputStream os = null;
            //-----------------------------

            try {

                URL url = new URL("http://"192.168.8.1"/webappcesfam/web/index.php?r=paciente/login-paciente"); //Inicia la conexion al webservice.
                try {
                    urlConnection = (HttpURLConnection) url.openConnection();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                urlConnection.setDoOutput(true);
                urlConnection.setRequestMethod("POST");
                urlConnection.setRequestProperty("Content-Type", "application/json");
                urlConnection.setRequestProperty("Accept", "application/json");
                urlConnection.connect();

                os = new BufferedOutputStream(urlConnection.getOutputStream());


                os.write(datos.toString().getBytes()); //empieza a enviar los datos al webservice
                os.flush();


                InputStream inputStream = urlConnection.getInputStream();


                StringBuffer buffer = new StringBuffer();
                reader = new BufferedReader(new InputStreamReader(inputStream));
                String inputLine = "";
                while ((inputLine = reader.readLine()) != null)
                {
                    buffer.append(inputLine);
                }

                JsonResponse = buffer.toString();


                JSONObject resultadoJSON = null;
                try {
                    resultadoJSON = new JSONObject(JsonResponse); //obtiene la respuesta desde el webservice en formato JSON, Siempre sera un par de datos : ID y los datos
                } catch (JSONException e) {
                    e.printStackTrace();
                }


                return resultadoJSON;


            } catch (IOException e) {
                Log.d("Session", "Error1: " + e.getMessage());
                e.printStackTrace();
            } finally {
                if (urlConnection != null) {
                    urlConnection.disconnect();
                }
                if (reader != null) {
                    try {
                        reader.close();
                    } catch (final IOException e) {
                        Log.d("Session", "Error3: " + e.getMessage());
                    }
                }
            }
            return null;
        }

        protected void onPostExecute(JSONObject respuestaOdata) //envias la respuesta del webservice a la clase principal en mi caso
        {
            Login l=(Login)ControllerActivity.actividadActual;
            l.recibirMensajeValdiacion(respuestaOdata);


        }
    }
}