Erro ao inserir dados no mysql(Json+php+android)

estou com erro nesse codigo ele trava e fecha a aplicação por favor me ajudem

public class AddClientes extends Activity {

// Progress Dialog
private ProgressDialog pDialog;

JSONParser jsonParser = new JSONParser();
EditText inputplaca;
EditText inputnome;
EditText inputemail;



// url to create new product
private static String url_create_product= "http://192.168.0.123/sgeit/create_product.php";

// JSON Node names
private static final String TAG_SUCCESS = "success";

@Override
public void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	setContentView(R.layout.telacadastro);

	// Edit Text
	inputplaca = (EditText) findViewById(R.id.inputplaca);
	inputnome = (EditText) findViewById(R.id.inputnome);
	inputemail = (EditText) findViewById(R.id.inputemail2);
	

	// Create button
	Button btnCadastra = (Button) findViewById(R.id.btncadastra);

	//button click event
	btnCadastra.setOnClickListener(new View.OnClickListener() {

		@Override
		public void onClick(View view) {
			 //creating new product in background thread
			 new CriarnovoCliente().execute();
		}
	});
}

/**
 * Background Async Task to Create new product
 * */
class CriarnovoCliente extends AsyncTask<String, String, String> {

	/**
	 * Before starting background thread Show Progress Dialog
	 * */
	protected void onPreExecute() {
		super.onPreExecute();
		pDialog = new ProgressDialog(AddClientes.this);
		pDialog.setMessage("Cadastrando...");
		pDialog.setIndeterminate(false);
		pDialog.setCancelable(true);
		pDialog.show();
	}

	/**
	 * Creating product
	 * */
	protected String doInBackground(String... args) {
		String placa = inputplaca.getText().toString();
		String nome = inputnome.getText().toString();
		String email = inputemail.getText().toString();
	

		// Building Parameters
		List<NameValuePair> params = new ArrayList<NameValuePair>();
		params.add(new BasicNameValuePair("placa", placa));
		params.add(new BasicNameValuePair("nome", nome));
		params.add(new BasicNameValuePair("email", email));
	

		// getting JSON Object
		// Note that create cliente url accepts POST method
		JSONObject json = jsonParser.makeHttpRequest(url_create_product,
				"POST", params);
		
		// check log cat fro response
		Log.d("Create Response", json.toString());

		// check for success tag
		try {
			int success = json.getInt(TAG_SUCCESS);

			if (success == 1) {
				// successfully created cliente
				Intent i = new Intent(getApplicationContext(), MainActivity.class);
				startActivity(i);
				
				// closing this screen
				finish();

			} else {
				
			}
		} catch (JSONException e) {
			e.printStackTrace();
		}

		return null;
	}

	/**
	 * After completing background task Dismiss the progress dialog
	 * **/
	protected void onPostExecute(String file_url) {
		// dismiss the dialog once done
		pDialog.dismiss();
	}

}

}

Poste a stacktrace que aparece no console quando a aplicação quebra.