Start Print (Cmd: 128) crashes printer | OpenCentauri | Page 1

copper raven Mar 2, 2026, 1:05 AM

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I've been working on this, and every time I try to run the 128 start print, the printer crashes. When I go up to the printer, it's frozen on whatever screen it was on and needs to be turned off and back on to restart.

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import asyncio
import json
import time
import uuid
import websockets

PRINTER_IP = "myip"
FILE_NAME = "Cube.gcode"
MAINBOARDID = "myid"

async def start_print(ip: str, filename: str) -> None:
    req = {
        "Id": str(uuid.uuid4()),
        "Data": {
            "Cmd": 128,
            "Data": {"Filename": filename, "StartLayer": 0},
            "RequestID": str(uuid.uuid4()),
            "MainboardID": MAINBOARDID,
            "TimeStamp": int(time.time()),
            "From": 0,
        },
        "Topic": f"sdcp/request/{MAINBOARDID}",
    }

    async with websockets.connect(f"ws://{ip}:3030/websocket") as ws:
        await ws.send(json.dumps(req))
        print(await asyncio.wait_for(ws.recv(), timeout=3))


if __name__ == "__main__":
    asyncio.run(start_print(PRINTER_IP, FILE_NAME))

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This is the code that I'm using to run this from the documentation.
https://docs.opencentauri.cc/software/api/

copper raven Mar 2, 2026, 2:16 AM

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I did some more digging and tested whether I could get all the files on my printer, and it worked.

import asyncio
import json
import time
import uuid
import websockets

PRINTER_IP = "myip"
FILE_NAME = "Cube.gcode"
MAINBOARDID = "myid"

async def get_file(ip: int) -> dict:
    req = {
        "Id": str(uuid.uuid4()),
        "Data": {
            "Cmd": 258,
            "Data": {"Url": "/local/"},
            "RequestID": str(uuid.uuid4()),
            "MainboardID": MAINBOARDID,
            "TimeStamp": int(time.time()),
            "From": 0,
        },
        "Topic": f"sdcp/request/{MAINBOARDID}",
    }
    async with websockets.connect(f"ws://{ip}:3030/websocket") as ws:
        await ws.send(json.dumps(req))
        resp_raw = await asyncio.wait_for(ws.recv(), timeout=5)
        resp = json.loads(resp_raw)
        print(resp)

if __name__ == "__main__":
    asyncio.run(get_file(PRINTER_IP))

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Which gave me something like this, which confirms that the G-code is on the printer, and I can pull it using their API

{'Id': 'myid', 'Data': {'Cmd': 258, 'Data': {'Ack': 0, 'FileList': [  {'name': '/local//Cube.gcode', 'type': 1, 'CreateTime': 71, 'FileSize': 152651, 'LayerHeight': 0, 'TotalLayers': 81, 'EstFilamentLength': 0},]}, 'RequestID': 'id', 'MainboardID': 'mainboardid', 'TimeStamp': 1772417589}, 'Topic': 'sdcp/response/mainboardid'}

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Sorry for the bad code, and let me know what I can change to be able to run a print using their API

copper raven Mar 15, 2026, 4:46 AM

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any idea to be able to fix this?

subtle sand Mar 20, 2026, 12:39 AM

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Sorry, did not see this.

Can you check how the webui sends this via the network tab? @copper raven

copper raven Mar 21, 2026, 11:30 PM

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subtle sand Sorry, did not see this. Can you check how the webui sends this via the network...

I was able to fix the issue, I was missing the extra data information.

This is what I got from the webui
{"Id":"","Data":{"Cmd":128,"Data":{"Filename":"/local/Cube.gcode","StartLayer":0,"Calibration_switch":0,"PrintPlatformType":1,"Tlp_Switch":1},"RequestID":"","MainboardID":"","TimeStamp":1773968213890,"From":1}}

This was my working version

import asyncio, json, time, uuid, websockets

PRINTER_IP = ""
MAINBOARDID = ""
FILE_NAME = "/local/Cube.gcode"

#{"Id":"","Data":{"Cmd":128,"Data":{"Filename":"/local/Cube.gcode","StartLayer":0,"Calibration_switch":1,"PrintPlatformType":1,"Tlp_Switch":0},"RequestID":"","MainboardID":"","TimeStamp":1773972595979,"From":1}}

async def start_print(ip, filename):
    payload = {
        "Id": str(uuid.uuid4()),
        "Data": {
            "Cmd": 128,
            "Data": {
                "Filename": filename,
                "StartLayer": 0,
                "Calibration_switch": 0,
                "PrintPlatformType": 1,
                "Tlp_Switch": 0
            },
            "RequestID": str(uuid.uuid4()),
            "MainboardID": MAINBOARDID,
            "TimeStamp": int(time.time()),
            "From": 1,
        },
        "Topic": f"sdcp/request/{MAINBOARDID}"
    }

    async with websockets.connect(f"ws://{ip}:3030/websocket") as ws:
        await ws.send(json.dumps(payload))
        print(await asyncio.wait_for(ws.recv(), timeout=3))

if __name__ == "__main__":
    asyncio.run(start_print(PRINTER_IP, FILE_NAME))

subtle sand Mar 21, 2026, 11:31 PM

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🙏

#Start Print (Cmd: 128) crashes printer