.. _set_on_rt_log_alarm:

set_on_rt_log_alarm
------------------------------------------
This function registers a **callback** for the messages the controller sends about the **RT session**: an unsupported version, RT input not received within the set time, a missing heartbeat, and another RT client already connected.

Motion warnings and errors during RT control, including rejected RT commands, are reported through :ref:`set_on_log_alarm <set_on_log_alarm>`. Register both callbacks.

**Definition** |br|
``DRFLEx.h`` within class `CDRFLEx`, public section

.. code-block:: cpp

   void set_on_rt_log_alarm(TOnLogAlarmCB pCallbackFunc) {
       _set_on_rt_log_alarm(_rbtCtrlUDP, pCallbackFunc);
   };

**Parameter**

.. list-table::
   :widths: 25 25 50
   :header-rows: 1

   * - **Parameter Name**
     - **Data Type**
     - **Description**
   * - pCallbackFunc
     - :ref:`TOnLogAlarmCB <cb_tonlogalarmcb>` 
     - Function pointer to user-defined callback that handles  |br|
       log or alarm messages sent from the robot controller.

**Note**

- The callback executes automatically when the controller sends an RT session message.  
- See :ref:`Rules for callback functions <callback_rules>`.

**Example**

.. code-block:: cpp

   #include <chrono>
   #include <thread>

   // Define callback for alarm and log monitoring
   void OnRTLogAlarm(LPLOG_ALARM pLogAlarm) {
       printf("[RT LOG/ALARM] group %d, index %d: %s\n",
              pLogAlarm->_iGroup, pLogAlarm->_iIndex, pLogAlarm->_szParam[0]);
   }

   drfl.connect_rt_control("192.168.137.100", 12347);

   // Register real-time log and alarm callback
   drfl.set_on_rt_log_alarm(OnRTLogAlarm);

   // Configure and start RT control
   string version = "v1.0";
   float period = 0.001f;
   int losscount = 4;

   drfl.set_rt_control_input(version, period, losscount);
   drfl.set_rt_control_output(version, period, losscount);
   drfl.start_rt_control();

   // Keep the RT session open for 60 s; the callback runs when a message arrives
   const auto tEnd = std::chrono::steady_clock::now() + std::chrono::seconds(60);
   while (std::chrono::steady_clock::now() < tEnd) {
       std::this_thread::sleep_for(std::chrono::milliseconds(100));
   }

   drfl.disconnect_rt_control();

In this example, ``OnRTLogAlarm()`` prints each RT session message the controller sends.

**Tips**

- Useful for detecting RT input timeouts and session problems during live control.  
- Integrate with a GUI or network logger to visualize alarm states in real time.  
- When the controller ends the RT session, it reports an alarm to the :ref:`set_on_rt_log_alarm <set_on_rt_log_alarm>` callback, and RT data stops.
- Do not call ``get_rt_control_input_version_list``, ``get_rt_control_output_version_list``, ``get_rt_control_input_data_list``, ``get_rt_control_output_data_list`` or ``disconnect_rt_control`` from an RT callback; the call does not return. ``connect_rt_control`` called from an RT callback returns false and prints ``Already connected``.