.. _open_connection:

open_connection
------------------------------------------
This function connects to the robot controller over TCP/IP. TCP/IP is fixed internally, so it does not need to be specified. When two or more robot controllers are used, change the IP address in the T/P application.

If the controller does not respond, open_connection returns false.

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

.. code-block:: cpp

    bool open_connection(string strIpAddr = "192.168.137.100", unsigned int usPort= 12345) { return _open_connection(_rbtCtrl, strIpAddr.c_str(), usPort); };


**Parameter** 

.. list-table::
   :widths: 20 15 25 40
   :header-rows: 1

   * - **Parameter Name**
     - **Data Type**
     - **Default Value**
     - **Description**
   * - strIpAddr
     - string
     - "192.168.137.100"
     - Controller IP address to connect.
   * - usPort
     - unsigned int
     - 12345
     - Controller TCP port to connect.

**Return**

.. list-table::
   :widths: 10 20 70
   :header-rows: 1

   * - **Value**
     - **Type**
     - **Description**
   * - 0
     - int
     - Error — failed to establish a TCP/IP connection.
   * - 1
     - int
     - Success — successfully connected to the controller.

.. note::

   When a connection ends (``close_connection``, loss of connection, or ``open_connection`` on an object that is already connected), every callback registered with a ``set_on_*`` function is unregistered, except those registered with ``set_on_disconnected``, ``set_on_monitoring_ctrl_io_ex`` (with DRCF_VERSION 3, the default), ``set_on_rt_monitoring_data`` and ``set_on_rt_log_alarm``, which stay registered. After each successful ``open_connection``, register the other callbacks again and call ``setup_monitoring_version`` again. ``open_connection`` on a connected object closes the existing connection first and prints "Already connected : <ip>".

   If no data is received from the controller for about 2 seconds, the connection ends and the disconnect callback is called.

   When the address passed to ``open_connection`` is exactly "127.0.0.1", ``task_compliance_ctrl``, ``set_stiffnessx``, ``release_compliance_ctrl``, ``set_desired_force`` and ``release_force`` return true without sending the command to the controller.

   The controller accepts at most 10 TCP clients at a time, including the teach pendant. Connect the PC to the controller directly or through a routed network; connections through NAT or port forwarding are rejected during authentication.

**Example**

.. code-block:: cpp

   bool bConnected = drfl.open_connection("192.168.137.100");
   if (bConnected) {
       SYSTEM_VERSION tSysVerion = {};
       drfl.get_system_version(&tSysVerion);
       printf("System version: %s\n", tSysVerion._szController);
   }

This example connects the external PC to the robot controller using its IP address.  
When the connection is successful, it retrieves and prints the controller’s system version information.