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

Try it in the demo application

Everything on this page can be tried without writing code, in the Telnet page of the demo application.

The demo application is open source. The C# source of this page is TelnetControl.cs.

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