Resin Print Portal (RPP)

A web interface for managing and monitoring Elegoo resin 3D printers over WiFi. Tested on Elegoo Mars 4 Ultra.

Fork of RPP by JJtronics, built on Cassini by Vladimir Vukicevic.

Features

Upload .ctb / .goo slice files to the server
Send files to the printer and start printing in one step
Real-time print progress (layer counter + progress bar)
Pause, Resume and Stop a running print
Printer online/offline status indicator
Configure printer IP address or hostname via the web UI

File overview

`rpp.py` — Flask web server (main entry point)

The central application. Starts a Flask HTTP server on port 5001 and exposes the REST API that the browser calls:

Endpoint	Method	Description
`/`	GET	Serves the web interface (`index.html`)
`/get-printer-ip`	GET	Returns the currently configured printer IP
`/set-printer-ip`	POST	Saves a new printer IP to `printer_ip.txt`
`/print-status`	GET	Polls the printer status via Cassini and returns JSON with current layer, total layers, progress %, and online state
`/upload`	POST	Saves an uploaded `.ctb`/`.goo` file to the `uploads/` folder
`/files`	GET	Lists all files in `uploads/` with their size in MB
`/print-file`	POST	Starts a background thread that uploads the selected file to the printer and immediately starts the print
`/progress/<filename>`	GET	Returns upload/transfer progress for a running print job (0–100)
`/stop-print`	POST	Sends a stop command to the printer via Cassini
`/pause-print`	POST	Sends a pause command to the printer via Cassini
`/resume-print`	POST	Sends a resume command to the printer via Cassini
`/delete-file`	POST	Deletes a file from the `uploads/` folder

Print jobs run in a background thread with a mutex (print_lock) so only one job runs at a time.

`cassini.py` — Printer command-line interface

A CLI tool (also imported by rpp.py) that handles all communication with the printer. Originally written by Vladimir Vukicevic.

How it works:

Sends a UDP broadcast (M99999) on port 3000 to discover printers on the network.
Instructs the printer to connect to a temporary local MQTT server (M66666 <port>).
Over that MQTT connection, sends commands and receives status updates.
For file uploads, also starts a temporary HTTP server so the printer can pull the file by URL.

Available CLI commands:

Command	Description
`status`	Show current machine status, print progress, and layer count
`status-full`	Show the full raw JSON response from the printer
`watch`	Continuously poll and display print progress
`upload <file>`	Upload a `.ctb`/`.goo` file to the printer
`upload --start-printing <file>`	Upload and immediately start printing
`print <file>`	Start printing a file already stored on the printer
`stop`	Stop the current print
`pause`	Pause the current print
`resume`	Resume a paused print
`connect-mqtt <host:port>`	Point the printer at an external MQTT broker

rpp.py calls this script as a subprocess using the -p <ip> flag to target a specific printer.

`saturn_printer.py` — Printer protocol implementation

Implements the Elegoo SDCP protocol. Originally part of Cassini.

Discovery: broadcasts M99999 over UDP to find printers; parses the JSON response into a SaturnPrinter object.
Connection: sends M66666 <port> to make the printer connect to the local MQTT server.
Commands: encodes and sends JSON commands over MQTT topics /sdcp/request/<id> and reads replies from /sdcp/response/<id> and /sdcp/status/<id>.
File upload: registers the file on the built-in HTTP server, sends an UPLOAD_FILE command with the URL and MD5 checksum, then monitors download progress via status messages.
Print control: implements stop_print(), pause_print(), resume_print(), and print_file() with correct handling of all pause states (see table below).

Status enums used by the printer:

Enum	Values
`CurrentStatus`	READY (0), BUSY (1)
`PrintInfoStatus`	IDLE, PRINTING, EXPOSURE, RETRACTING, LOWERING, PAUSED_HW (7), PAUSED_LIFTED (8), STOPPING, STOPPED, PAUSED (14), COMPLETE (16)
`FileStatus`	NONE, DONE, ERROR

`simple_mqtt_server.py` — Embedded MQTT broker

A minimal MQTT broker written from scratch using Python asyncio. The Elegoo printer requires an MQTT connection to receive commands — this server provides that without needing an external broker like Mosquitto.

Supports: CONNECT, CONNACK, PUBLISH, PUBACK, SUBSCRIBE, SUBACK, DISCONNECT. Binds on a random free port each time so multiple sessions don't conflict.

`simple_http_server.py` — Embedded HTTP file server

A minimal async HTTP server used to serve the print file to the printer during upload. The printer fetches the file itself over HTTP after receiving the URL in the upload command.

Computes MD5 and file size when a route is registered — these are sent to the printer as part of the upload command so it can verify integrity. Binds on a random free port.

`templates/index.html` — Web interface

Single-page HTML interface with two cards:

Printer card: shows online/offline status, the configured IP (editable), current print status text, a progress bar, and Pause/Resume/Stop buttons (visible only during an active print).
Files card: table of uploaded files with name and size. Buttons to Upload, Print, and Delete.

`static/script.js` — Frontend logic

All browser-side behaviour:

On load: fetches printer IP, current print status, and file list.
Polls /print-status every 5 seconds to update the progress bar and control buttons.
File upload uses XMLHttpRequest with upload.onprogress for a real-time upload percentage overlay.
After triggering a print, polls /progress/<filename> every second until the transfer reaches 100%.
Pause/Resume/Stop call their respective endpoints and refresh the status afterwards.
The Pause button is hidden when paused; the Resume button is shown instead.

`static/styles.css` — Stylesheet

Dark-theme CSS for the web interface. Card layout, progress bar styling, button states, and the loading overlay with spinner.

`printer_ip.txt` — Printer address

Plain-text file containing the IP address or hostname of the printer. Read on every request by rpp.py; written when the user saves a new address via the web UI. Not committed to git (contains your local network config).

`rpp.service` — Systemd service unit

Runs rpp.py as a systemd service under the www-data user, restarting automatically on failure. Working directory is /opt/RPP.

`install.sh` — Installation script

One-shot setup: installs dependencies (git, python3-pip, python3-flask, alive-progress), clones the repo to /opt/RPP, sets permissions on uploads/ and printer_ip.txt, and enables + starts the systemd service.

`update.sh` — Update script

Pulls the latest version from GitHub (git reset --hard HEAD && git pull), and resets permissions on the writable files. Run manually when a new version is available.

`requirements.txt`

Python dependencies beyond the standard library and Flask (which is installed via apt):

alive-progress==3.1.4

Used for animated progress bars in the CLI. Not required for the web interface.

Installation

Tested on Ubuntu 24.04.

Install dependencies:

sudo apt update
sudo apt install git python3-pip python3-flask
sudo pip3 install alive-progress --break-system-packages

Clone the repository:

cd /opt/
git clone https://github.com/MichielBruijn/RPP.git
cd RPP

Set permissions:

sudo chmod 775 /opt/RPP/uploads /opt/RPP/printer_ip.txt
sudo chown www-data:www-data /opt/RPP/uploads /opt/RPP/printer_ip.txt

Optional — set printer IP now:

echo 192.168.1.50 > printer_ip.txt

Install and start the service:

sudo mv rpp.service /etc/systemd/system/
sudo systemctl enable rpp
sudo systemctl start rpp
sudo systemctl status rpp

The interface runs on port 5001. Use a reverse proxy (nginx, Apache) to expose it on port 80/443.

Update

cd /opt/RPP/
sudo git reset --hard HEAD
sudo git pull
sudo chmod 775 /opt/RPP/uploads /opt/RPP/printer_ip.txt
sudo chown www-data:www-data /opt/RPP/uploads /opt/RPP/printer_ip.txt
sudo systemctl restart rpp

Notes on pause and stop

The Elegoo SDCP protocol has three distinct paused states:

State	Cause	How to resume
PAUSED_LIFTED (8)	RPP Pause button	RPP Resume button
PAUSED_HW (7)	Pause via printer touchscreen	RPP Resume button or printer display
PAUSED (14)	RPP Stop button	Print is abandoned — start a new one

Pressing Stop in RPP sends a stop command and the printer ends the current print. The printer firmware briefly reports state 14 before returning to idle.

Credits

Original RPP by JJtronics
Cassini by Vladimir Vukicevic
Licensed under MIT

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Repository files navigation

Resin Print Portal (RPP)

Features

File overview

`rpp.py` — Flask web server (main entry point)

`cassini.py` — Printer command-line interface

`saturn_printer.py` — Printer protocol implementation

`simple_mqtt_server.py` — Embedded MQTT broker

`simple_http_server.py` — Embedded HTTP file server

`templates/index.html` — Web interface

`static/script.js` — Frontend logic

`static/styles.css` — Stylesheet

`printer_ip.txt` — Printer address

`rpp.service` — Systemd service unit

`install.sh` — Installation script

`update.sh` — Update script

`requirements.txt`

Installation

Update

Notes on pause and stop

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Name		Name	Last commit message	Last commit date
Latest commit History 72 Commits
SCREENSHOTS		SCREENSHOTS
static		static
templates		templates
.gitignore		.gitignore
LICENSE		LICENSE
README.md		README.md
cassini.py		cassini.py
install.sh		install.sh
printer_ip.txt		printer_ip.txt
requirements.txt		requirements.txt
rpp.py		rpp.py
rpp.service		rpp.service
saturn_printer.py		saturn_printer.py
simple_http_server.py		simple_http_server.py
simple_mqtt_server.py		simple_mqtt_server.py
update.sh		update.sh

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Resin Print Portal (RPP)

Features

File overview

rpp.py — Flask web server (main entry point)

cassini.py — Printer command-line interface

saturn_printer.py — Printer protocol implementation

simple_mqtt_server.py — Embedded MQTT broker

simple_http_server.py — Embedded HTTP file server

templates/index.html — Web interface

static/script.js — Frontend logic

static/styles.css — Stylesheet

printer_ip.txt — Printer address

rpp.service — Systemd service unit

install.sh — Installation script

update.sh — Update script

requirements.txt

Installation

Update

Notes on pause and stop

Credits

About

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`rpp.py` — Flask web server (main entry point)

`cassini.py` — Printer command-line interface

`saturn_printer.py` — Printer protocol implementation

`simple_mqtt_server.py` — Embedded MQTT broker

`simple_http_server.py` — Embedded HTTP file server

`templates/index.html` — Web interface

`static/script.js` — Frontend logic

`static/styles.css` — Stylesheet

`printer_ip.txt` — Printer address

`rpp.service` — Systemd service unit

`install.sh` — Installation script

`update.sh` — Update script

`requirements.txt`

Packages