I reverse engineered my 3D printer’s LAN protocol and turned it into a Home Assistant integration

I reverse engineered my 3D printer’s LAN protocol and turned it into a Home Assistant integration

I recently wanted something very simple: I wanted my Anycubic Kobra X 3D printer to show up properly in Home Assistant.

Not through a cloud integration. Not through a vendor dashboard. Just local LAN visibility inside my own smart home setup.

At first, I only wanted to read basic status information: printer state, nozzle temperature, bed temperature, fan speed, camera availability, and filament information. But as I started digging, I found that the printer already exposes a lot of useful local communication. The challenge was understanding how it worked.

The starting point

The official slicer can talk to the printer over LAN, so I knew the data had to be there somewhere.

That led me down the reverse engineering path:

• Downloading and inspecting the web workbench assets
• Reading JavaScript sourcemaps
• Finding the LAN MQTT helper code
• Figuring out credential discovery
• Mapping MQTT topics and payloads
• Testing raw LAN messages against the printer
• Comparing printer reports with what the slicer UI showed

Eventually, I found enough of the local protocol to build a Home Assistant integration around it.

What the integration does now

The first release focuses on practical Home Assistant use cases:

• Local setup by printer IP
• Printer state
• Nozzle and bed temperatures
• Target temperature controls
• Fan speed monitoring and control
• Camera availability
• Camera light control
• Multi-color box status
• Dynamic filament slot sensors
• Refresh and reconnect buttons
• Diagnostics support

I intentionally left out more dangerous or context-sensitive actions like moving axes, uploading files, starting prints, or filament loading/unloading. Those are better handled from the slicer, where you are actively supervising the printer.

The goal is not to replace the slicer. The goal is to make the printer visible and manageable in Home Assistant.

Keeping research and implementation separate

I decided to split the project into two repositories.

The Home Assistant integration repository is clean and focused on the HACS implementation:

https://github.com/grunna/ha-anycubic-kobra-x-lan

The reverse engineering notes, protocol research, and test scripts are kept separately:

https://gitlab.com/grunna/anycubic-kobra-x-lan

That separation made the public integration much easier to understand and review, while still keeping the research available for anyone who wants to verify or extend the protocol work.

Current status

The integration works locally for my Anycubic Kobra X and has been submitted for HACS review.

The camera stream still needs more investigation because the slicer appears to use an FLV-based player flow, while Home Assistant’s normal camera card expects something different. But the rest of the integration is already useful for monitoring, dashboarding, and basic printer control.

What I learned

The biggest lesson was that reverse engineering does not always mean packet captures and guesswork. Sometimes the best source of truth is the vendor’s own frontend code.

The slicer already knew:

• Which MQTT topics to use
• Which payloads to send
• How reports were structured
• How lights, fans, temperatures, filament boxes, and camera state worked

Once I found that, the project became much more about carefully translating that behavior into a Home Assistant integration.

It was a fun reminder that small personal automation problems can turn into useful open source projects.