connect_rt_control

This function establishes a UDP/IP connection between the external PC and the robot controller to enable Real-time External Control (RT) communication.
This channel is independent of the original TCP/IP API, and control authority does not apply to it.
For the integrated controller (v3), versions v3.3 or below can be connected to 192.168.137.50.

Definition
DRFLEx.h within class CDRFLEx, public section

bool connect_rt_control(string strIpAddr = "192.168.137.100",
                        unsigned int usPort = 12347) {
    return _connect_rt_control(_rbtCtrlUDP, strIpAddr.c_str(), usPort);
};

Parameter

Parameter Name	Data Type	Default Value	Description
strIpAddr	string	"192.168.137.100"	Target controller IP address for the UDP connection. Pass the controller address as a dotted IPv4 string (for example "192.168.137.100").
usPort	unsigned int	12347	Port number for RT communication (default UDP port).

Return

Value	Description
1	The controller completed the connect handshake.
0	The RT channel is not connected. Causes: the UDP socket cannot be opened; the controller does not answer within about 5 seconds; the connection drops during the handshake; the set_rt_thread_priority setting cannot be applied; the library cannot start its real-time processing; real-time control is already connected (the library prints Already connected); or the function is called from inside a real-time callback (the library prints connect_rt_control() cannot be called from an RT callback). Except for the last two cases, the function closes the RT channel before returning, and a later call can connect again.

Caution

• Do not call this function from inside a real-time callback, such as the one registered with set_on_rt_monitoring_data. It returns 0 there.

• If the controller does not answer, for example because the IP address or port is wrong, or because another RT client is already connected to the controller, the function returns 0 after about 5 seconds.

Typical usage

• Connect before configuring RT control input/output schema and period.

• Used as the first step of any real-time joint or task control loop.

Note

• Real-time external control uses UDP/IP communication, not TCP/IP.

• This channel runs independently of the TCP/IP API connection. It has no commands for control authority or safety settings; use the TCP/IP API for those.

• On integrated controllers (v3.x) up to v3.3, the RT server accepts connections on every controller address, including 192.168.137.50. From v3.4, it accepts them only on the API address (default 192.168.137.100).

• Default configuration supports 1-to-1 UDP communication between controller and external PC.

• When the controller ends the RT session, it reports an alarm to the set_on_rt_log_alarm callback, and RT data stops.

• RT has no disconnect notification. To detect a lost RT link, check that time_stamp in read_data_rt or the RT callback keeps advancing.

• After disconnect_rt_control, the RT channel can be connected again in the same process.

• To see why the connection fails, register set_on_rt_log_alarm before calling this function.

• If the real-time connection closes, wait at least 5 seconds before calling this function again. On the simulator, restart the simulator instead.

Example

// Connect to the robot controller via UDP for RT control
if (drfl.connect_rt_control("192.168.137.100", 12347)) {
    printf("RT connection established successfully.\n");

    // Ready to configure input/output schema and start RT streaming
    drfl.start_rt_control();
}
else {
    printf("RT connection failed.\n");
}

In this example, the function establishes a UDP connection with the controller to prepare for real-time motion control or high-frequency data exchange. Once connected, users can call start_rt_control to begin RT streaming.

Tips

• Ensure the robot is powered and reachable on the specified IP before calling this function.

• Close the RT channel gracefully using disconnect_rt_control after operations.

• In real-time applications, this step should be followed by setting the input/output version and period using set_rt_control_input and set_rt_control_output.