send a webhook message everytime print starts klipper

Charlotte

3 min read

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01-03-2025

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Klipper, the popular 3D printer firmware, offers incredible flexibility and control. One often-requested feature is automated notifications. This article explains how to send a webhook message to a service like Discord, Slack, or your own custom application every time a print starts in Klipper. This provides real-time updates on your prints, eliminating the need to constantly monitor your printer.

Setting up the Klipper Configuration

This process leverages Klipper's powerful scripting capabilities. We'll use a Python script to execute the webhook POST request. First, you'll need to add the following lines to your printer.cfg file within your Klipper configuration:

[gcode_macro_send_webhook]
gcode:
  {% set url = params.url %}
  ; Replace with your actual webhook URL
  RUN_COMMAND: "python3 /path/to/your/webhook_script.py {url}"

Important:

• Replace /path/to/your/webhook_script.py with the actual path to your Python script.
• Replace {url} with the actual URL to your webhook service. This will typically involve an API key or similar authentication method.

Ensure that Python 3 is installed on your Klipper host system and accessible via the command line. The script path must be correctly specified; otherwise, Klipper will fail to execute the script.

Creating the Python Webhook Script (webhook_script.py)

Create a Python file named webhook_script.py (or similar) and place it in the directory you specified in your printer.cfg file. This script will handle the sending of the webhook request. Here's a basic example using the requests library:

import requests
import sys

def send_webhook(url):
    try:
        payload = {
            "content": "3D Print Started!"  # Customize your message here
        }
        headers = {
            'Content-Type': 'application/json'
        }
        response = requests.post(url, json=payload, headers=headers)
        response.raise_for_status() # Raise HTTPError for bad responses (4xx or 5xx)
        print(f"Webhook sent successfully: {response.status_code}")
    except requests.exceptions.RequestException as e:
        print(f"Error sending webhook: {e}")

if __name__ == "__main__":
    url = sys.argv[1]
    send_webhook(url)

Remember to install the requests library: pip3 install requests

This script takes the webhook URL as a command-line argument and sends a JSON payload containing a simple "Print Started!" message. You can customize this message to include additional details, such as the file being printed or the estimated print time. For more complex scenarios, you might need to adjust the payload structure to match your webhook service's API requirements.

Integrating with Your Print Start G-Code

Now, you need to call the send_webhook macro whenever a print starts. You can do this by adding a call to the macro in your start gcode. Modify your start_gcode section in printer.cfg to include the following:

[gcode_macro start_print]
gcode:
  SEND_WEBHOOK url=<your_webhook_url>
  ; Your existing start_gcode commands

Replace <your_webhook_url> with your actual webhook URL. Now, every time you start a print using the START_PRINT command (or any other macro that calls START_PRINT), this script will execute, sending the notification.

Troubleshooting Tips

• Check your Python path: Make sure the Python executable is correctly identified in your Klipper configuration.
• Verify the webhook URL: Double-check for typos in the URL and ensure that the URL is correctly formatted for your webhook service.
• Inspect the Klipper logs: If the script isn't running, check the Klipper logs for error messages.
• Test the script independently: Run the Python script directly from the command line to ensure it's functioning correctly before integrating it into Klipper.
• Firewall issues: Ensure that your firewall isn't blocking outgoing connections from your Klipper host.

Advanced Customization

• Include print details: Modify the Python script to include the filename, estimated print time, or other relevant information in the webhook message. This can be achieved by accessing Klipper variables within your script (refer to Klipper documentation for variable access).
• Error handling: Implement more robust error handling in the Python script to gracefully manage network issues or webhook failures.
• Different webhook services: Adapt the script and payload to integrate with various webhook platforms (Discord, Slack, IFTTT, etc.). Each service has unique API requirements.

This comprehensive guide enables you to receive real-time notifications every time a print starts in Klipper. Enjoy automated updates and a more streamlined 3D printing workflow!