function _sim_join()
{
    $stationId = $_POST['stationId'];
    $stationType = $_POST['stationType'];
    $json = array("message_version" => 0, "station_type" => $stationType, "station_url" => $_POST['station_url']);
    // hack just to reuse do_post_request code
    $json = RPI::do_post_request("http://localhost/m/rpi/join/{$stationId}", $json);
    if ($json === false) {
        mock_set_rpi_response("error");
    } else {
        mock_set_rpi_response(json_encode($json));
    }
    redirect("mock_rpi/index", "done with join ");
}
function _sim_submit()
{
    $stationId = $_POST['stationId'];
    $candidate_answer = $_POST['candidate_answer'];
    $is_correct = isset($_POST['is_correct']) ? true : false;
    $fail_message = $_POST['fail_message'];
    $json = array("message_version" => 0, "candidate_answer" => $candidate_answer, "is_correct" => $is_correct, "fail_message" => $fail_message);
    // hack just to reuse do_post_request code
    $json = RPI::do_post_request("http://localhost/m/rpi/submit/{$stationId}", $json);
    if ($json === false) {
        mock_set_rpi_response("error");
    } else {
        mock_set_rpi_response(json_encode($json));
    }
    redirect("mock_rpi/index", "done with submit ");
}