pycentauri 0.4.0

Python client and MCP server for Elegoo Centauri Carbon 3D printers

pycentauri

Python client, CLI, and MCP server for the Elegoo Centauri Carbon 3D printer.

pycentauri speaks the printer's native SDCP v3 protocol over its local WebSocket (port 3030) — no cloud account required. It exposes six surfaces:

1. An async Python library for direct integration.
2. A centauri CLI for quick status checks, snapshots, and control.
3. An MCP server so AI agents (Claude Code, Claude Desktop, Cursor, any MCP-compatible client) can monitor and drive the printer as a tool.
4. An HTTP + SSE server for dashboards, reverse-proxy integration, and anything that wants a plain REST API.
5. A built-in web UI (industrial instrument-panel theme, mobile-friendly) served at /ui/ by the HTTP server.
6. An RTSP bridge that re-streams the printer's MJPEG webcam as H.264/RTSP for Home Assistant, Jellyfin, VLC, Frigate, and NVRs.

Status: alpha. The protocol has been reverse-engineered from the official elegoo-link C++ SDK and the CentauriLink project. It works against the original Centauri Carbon on current firmware. The newer Centauri Carbon 2 (which uses MQTT) is not supported.

Install

pip install pycentauri                    # library + CLI
pip install "pycentauri[mcp]"             # + MCP server
pip install "pycentauri[server]"          # + HTTP REST/SSE server
pip install "pycentauri[mcp,server]"      # everything

Quick start — CLI

# Find printers on your LAN
centauri discover

# One-shot status (pretty or JSON)
centauri status --host 192.168.1.209
centauri status --host 192.168.1.209 --json

# Stream live status updates
centauri watch --host 192.168.1.209

# Grab a webcam snapshot
centauri snapshot --host 192.168.1.209 shot.jpg

# Files on the printer
centauri files --host 192.168.1.209

# Control actions require --enable-control
centauri print start cube.gcode --host 192.168.1.209 --enable-control
centauri print pause              --host 192.168.1.209 --enable-control
centauri print resume             --host 192.168.1.209 --enable-control
centauri print stop               --host 192.168.1.209 --enable-control

The host can also come from PYCENTAURI_HOST or ~/.config/pycentauri/config.toml.

Quick start — Python

import asyncio
from pycentauri import Printer

async def main():
    async with await Printer.connect("192.168.1.209") as printer:
        status = await printer.status()
        print(status.state, status.progress, status.temp_nozzle)

        jpeg = await printer.snapshot()
        with open("shot.jpg", "wb") as f:
            f.write(jpeg)

        async for update in printer.watch():
            print(update.state, update.progress)

asyncio.run(main())

Quick start — HTTP server

# Read-only, bound to loopback so only this box can hit it:
centauri server --host 192.168.1.209 --port 8787

# Read + write, bound to all interfaces (put a reverse proxy in front):
centauri server --host 192.168.1.209 --bind 0.0.0.0 --port 8787 --enable-control

Method	Path	Notes
GET	/	Redirects to /ui/
GET	/ui/	Built-in web dashboard
GET	/api/info	Health + version (JSON)
GET	/status	Latest status push (cached; updates every ~5s)
GET	/attributes	Printer attributes
GET	/snapshot	image/jpeg response
GET	/stream	MJPEG stream proxied from the printer (embeds in <img>)
GET	/discover	LAN scan
GET	/events/status	Server-Sent Events stream of pushes
POST	/print/start	Body: {"filename": "cube.gcode"}. Requires --enable-control.
POST	/print/{pause,resume,stop}	Requires --enable-control.

The server holds a single long-lived WebSocket to the printer and reuses it for every request — no per-request reconnect, and it won't bump into the firmware's 5-slot limit.

Quick start — RTSP bridge

# Install dependencies first:
#   mediamtx  https://github.com/bluenviron/mediamtx/releases  (or `brew install mediamtx`)
#   ffmpeg    `brew install ffmpeg` or `apt install ffmpeg`

# Standalone: foreground, Ctrl-C to stop
centauri rtsp --host 192.168.1.209
# → rtsp://<this-host>:8554/printer

# Or, integrated with the HTTP server + web UI
centauri server --host 192.168.1.209 --rtsp --bind 0.0.0.0
# Web UI gains a STREAM panel with a toggle, a copy-URL button, and live status
# at http://<this-host>:8787/ui/

Open that URL in VLC (Media → Open Network Stream), point Home Assistant at it via the Generic Camera integration, or feed it to Frigate / Jellyfin / Synology Surveillance for NVR recording and motion detection.

MediaMTX runs the ffmpeg transcode only while at least one client is actually connected, so idle cost is zero. Tunable: --fps, --bitrate, --preset, --path, --port, --bind. Run centauri rtsp --help (or centauri server --help) for the full list.

Quick start — MCP

Register the server with your agent. With Claude Code:

claude mcp add pycentauri -- python -m pycentauri.mcp
# or, with control actions enabled (gives the agent start/pause/stop/upload):
claude mcp add pycentauri -- python -m pycentauri.mcp --enable-control

Set PYCENTAURI_HOST in your MCP server env so the agent can't target an arbitrary IP. The server exposes these tools:

Tool	Always available	Description
get_status	yes	State, temperatures, progress, elapsed/remaining
get_attributes	yes	Model, firmware, mainboard ID
list_files	yes	Files stored on the printer
get_snapshot	yes	Webcam frame as MCP Image content
discover_printers	yes	LAN scan
start_print	only with --enable-control	Starts a print
pause_print	only with --enable-control	Pauses the current print
resume_print	only with --enable-control	Resumes a paused print
stop_print	only with --enable-control	Stops the current print
upload_file	only with --enable-control	Uploads a file to the printer

Safety

Control actions are gated behind an explicit enable_control=True (library) or --enable-control flag (CLI / MCP). Destructive MCP tools are not even registered when the flag is off, so an LLM never sees them. Still: leaving a printer running unattended with write-capable agents is your responsibility.

Known firmware quirks

• 5 concurrent WebSocket connections max. The printer's SDCP server accepts up to 5 open WebSockets on port 3030; the 6th returns HTTP 500 with body "too many client". Slots release immediately when a connection closes — the CLI and MCP server each open/close one per invocation, so this is almost never a problem in practice.
• Paused / errored states don't auto-push Attributes. The printer only sends its Attributes frame spontaneously while idle or printing. In paused and errored states it stays silent until asked. Since every SDCP command needs the printer's MainboardID, the client takes care of this by pre-seeding the mainboard ID from a UDP discovery on every connect (as of v0.1.1). If you call Printer.connect() directly without discovery, pass mainboard_id= yourself.

Credits & licensing

• Protocol reference: elegoo-link (Apache-2.0) and CentauriLink.
• pycentauri is licensed under Apache-2.0. See LICENSE.
• Not affiliated with or endorsed by Elegoo.