Telnet overview

Telnet KCL is a text-based protocol that lets you send commands to a Fanuc robot controller. It requires no paid option and is available on all controllers and ROBOGUIDE.

Key features

• Program control: Run, pause, hold, continue, abort programs
• Variable access: Read and write system variables
• I/O control: Set output ports, simulate and unsimulate inputs
• Alarm management: Reset alarms and errors
• Debugging: Add breakpoints, step through code line by line
• Custom commands: Send any raw KCL command

Prerequisites

Telnet must be enabled on your robot controller. See Enable Telnet on your robot for setup instructions.

Quick example

using UnderAutomation.Fanuc;
using UnderAutomation.Fanuc.Telnet;

  public class Telnet
  {
    static void Main()
    {
      // Create a new Fanuc robot instance
      FanucRobot robot = new FanucRobot();

      // Set connection parameters
      ConnectionParameters parameters = new ConnectionParameters("192.168.0.1");
      parameters.Telnet.Enable = true;
      parameters.Telnet.TelnetKclPassword = "TELNET_PASS";

      // Connect to the robot
      robot.Connect(parameters);

      
      // Reset alarms
      robot.Telnet.Reset();

      // Run a program
      robot.Telnet.Run("MyProgram");
      robot.Telnet.Pause("MyProgram");
      robot.Telnet.Hold("MyProgram");
      robot.Telnet.Continue("MyProgram");
      robot.Telnet.Abort("MyProgram", force: true);

      // Set a variable
      robot.Telnet.SetVariable("$RMT_MASTER", 1);

      // Set an output port (example: DOUT port 2 = 0)
      robot.Telnet.SetPort(KCLPorts.DOUT, 2, 0);

      // Simulate an input port (example: DIN port 3 = 1)
      robot.Telnet.Simulate(KCLPorts.DIN, 3, 1);
      robot.Telnet.Unsimulate(KCLPorts.DIN, 3);
      
    }

  }

Connection

static void Main()
{
// Via FanucRobot
var robot = new FanucRobot();
var parameters = new ConnectionParameters("192.168.0.1");
parameters.Telnet.Enable = true;
parameters.Telnet.TelnetKclPassword = "your_password";
robot.Connect(parameters);

// Or standalone
var telnet = new TelnetClient();
telnet.Connect("192.168.0.1", "your_password");
}
}

For ROBOGUIDE, pass the workcell folder path instead of an IP address. The SDK reads services.txt to find the correct Telnet port.

Events

The Telnet client raises events for real-time monitoring:

• MessageReceived : Fired when a message is received from the controller
• RawDataReceived : Raw byte data from the TCP socket
• ErrorOccured : Connection or communication errors
• CommandSent / CommandReceived : Track sent and received KCL commands
• TpCoordinatesReceived : Teach pendant coordinate system changes

Check if Telnet is available

Via FTP, you can check if Telnet is available on the controller:

parameters.Ftp.FtpPassword = "";
robot.Connect(parameters);
Features features = robot.Ftp.GetSummaryDiagnostic().Features;
bool isTelnetAvailable = features.HasTelnet;
}
}

Limitations

• Text-based protocol: Slower than binary protocols like SNPX for bulk data operations
• Sequential commands: Commands are sent one at a time over a single TCP connection
• No bulk register read: Variable reading is done by name, not by index. Use SNPX, FTP or CGTP for reading registers in bulk

Next steps

• Program control : Run, pause, abort programs
• Variables & I/O : Read/write variables and control ports
• Debugging & breakpoints : Step-by-step debugging

API reference