Android - Conexión a una red local

public class BackgroundWorker extends AsyncTask<String,Void,String> {

    Context context;

    AlertDialog alertDialog;

    public BackgroundWorker(Context ctx){

        this.context = ctx;

    }

    @Override

    protected String doInBackground(String... params) {

        String registrar_url = "http://192.168.0.4/APPGeoAlertAR/Registrar.php";

        String type = params[0];

        if (type.equals("registrar")) {

            String patente = params[1];

            String direccion = params[2];

            String latitud = params[3];

            String longitud = params[4];

            try {

                URL url = new URL(registrar_url);

                HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();

                httpURLConnection.setRequestMethod("POST");

                httpURLConnection.setDoOutput(true);

                httpURLConnection.setDoInput(true);

                OutputStream outputStream = httpURLConnection.getOutputStream();

                httpURLConnection.connect();

                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));

                String post = URLEncoder.encode("lugarRobo","UTF-8")+"="+URLEncoder.encode(direccion,"UTF-8")+"&"+URLEncoder.encode("ultimaLat","UTF-8")+"="+URLEncoder.encode(latitud,"UTF-8")+"&"+URLEncoder.encode("ultimaLon","UTF-8")+"="+URLEncoder.encode(longitud,"UTF-8")+"&"+URLEncoder.encode("idPropietario","UTF-8")+"="+URLEncoder.encode(patente,"UTF-8");

                bufferedWriter.write(post);

                bufferedWriter.flush();

                bufferedWriter.close();

                outputStream.close();

                InputStream inputStream = httpURLConnection.getInputStream();

                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream,"iso-8859-1"));

                String result = "";

                String line = "";

                while ((line = bufferedReader.readLine()) != null){

                    result += line;

                }

                bufferedReader.close();

                httpURLConnection.disconnect();

                return result;

            } catch (MalformedURLException e) {

                e.printStackTrace();

            } catch (IOException e) {

                e.printStackTrace();

            }

        }

        return null;

    }

    @Override

    protected void onPreExecute() {

        alertDialog = new AlertDialog.Builder(context).create();

        alertDialog.setTitle("Login Status");

    }

    @Override

    protected void onPostExecute(String result) {

        alertDialog.setMessage(result);

        alertDialog.show();

    }

    @Override

    protected void onProgressUpdate(Void... values) {

        super.onProgressUpdate(values);

    }

}

catch (MalformedURLException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

catch (MalformedURLException e) {

textView.setText ( e.toString( ) );

} catch (IOException e) {

textView.setText ( e.toString( ) );

} catch (Exception e) {

textView.setText ( e.toString( ) );

}