Failed to establish temporary connection Adventurer 3C

[crislobo-alt]

I used to be able to slice and upload prints from orcaslicer. This strangely stopped working recently. (The printer reads something about a format error.) Later, I attempted to just put the gcode on a flash drive, and the printer refused to see it, but the folders on the drive were present. It used to read gcode just fine? I attempted using Flashforge-UI and I got "Failed to establish temporary connection," and I tried running it headless too:

.\FlashForgeUI.exe --enable-logging --headless --printers="192.168.1.235:legacy"
PS C:\Users\Cristobal\AppData\Local\Programs\FlashForgeUI>
[Bootstrap] App name set to "FlashForgeUI"
[Bootstrap] userData path: C:\Users\Cristobal\AppData\Roaming\FlashForgeUI
[CameraProxyService] Multi-context camera proxy service initialized
[RtspStreamService] RTSP stream service created
Failed to load config file: SyntaxError: Unexpected end of JSON input
    at JSON.parse (<anonymous>)
    at ConfigManager.loadFromFile (C:\Users\Cristobal\AppData\Local\Programs\FlashForgeUI\resources\app.asar\lib\managers\ConfigManager.js:240:41)
Config loading complete - emitting config-loaded event
[RtspStreamService] Initializing RTSP stream service
[RtspStreamService] ffmpeg not found in any location
[RtspStreamService] Searched paths: [
  'ffmpeg',
  '/opt/homebrew/bin/ffmpeg',
  '/usr/local/bin/ffmpeg',
  '/opt/local/bin/ffmpeg',
  '/usr/bin/ffmpeg',
  '/snap/bin/ffmpeg',
  '/var/lib/flatpak/exports/bin/ffmpeg',
  '~/.local/share/flatpak/exports/bin/ffmpeg',
  '/usr/local/bin/ffmpeg',
  '~/bin/ffmpeg',
  'C:\\ffmpeg\\bin\\ffmpeg.exe',
  'C:\\Program Files\\ffmpeg\\bin\\ffmpeg.exe',
  'C:\\Program Files (x86)\\ffmpeg\\bin\\ffmpeg.exe'
]
[RtspStreamService] Install ffmpeg to enable RTSP camera viewing:
[RtspStreamService]   - macOS: brew install ffmpeg
[RtspStreamService]   - Ubuntu/Debian: sudo apt install ffmpeg
[RtspStreamService]   - Fedora/RHEL: sudo dnf install ffmpeg
[RtspStreamService]   - Arch: sudo pacman -S ffmpeg
[RtspStreamService]   - Windows: Download from ffmpeg.org
[RtspStreamService] ffmpeg not available - RTSP streaming will not work
[RtspStreamService] Install ffmpeg to enable RTSP camera viewing
[Headless] RTSP stream service initialized
[Headless] Spoolman integration service initialized
[MultiContextTemperatureMonitor] Initialized
[Headless] Multi-context temperature monitor initialized
[MultiContextSpoolmanTracker] Initialized
[Headless] Multi-context Spoolman tracker initialized
[Headless] Skipping notification system initialization
[Headless] Notification system initialized
[MultiContextNotificationCoordinator] Initialized
[Headless] Multi-context notification coordinator initialized
[DiscordNotificationService] Initialized
No printer details file found - starting fresh
[MultiContextPollingCoordinator] Context manager listeners registered
[2026-03-08 18:37:58] [Headless] Starting FlashForgeUI in headless mode
WebUI serving static files from: C:\Users\Cristobal\AppData\Local\Programs\FlashForgeUI\resources\webui\static
WebUI static file middleware configured successfully
WebSocket server subscribed to Spoolman events
WebSocket server initialized
[2026-03-08 18:37:58] [Headless] Connecting to 1 explicitly specified printer(s)...
[Headless] Connecting directly to 192.168.1.235 (legacy)
TcpPrinterClient creation
Connected
(Legacy API) InitControl()
sendCommand: ~M601 S1
CheckSocket()
WebUI server running at http://192.168.1.160:3000
sendCommand: ~M602
CheckSocket()
sendCommand: ~M601 S1
CheckSocket()
sendCommand: ~M115
CheckSocket()
PrinterInfo replay has null firmware version
(Legacy API) Failed to get printer info, aborting.
[Headless] Failed to connect to 192.168.1.235: Failed to establish temporary connection
[2026-03-08 18:37:58] [Headless] ERROR: No printers connected
[2026-03-08 18:37:58] [Headless] ERROR: No printers connected
[2026-03-08 18:37:58] [Headless] WebUI server already running
[2026-03-08 18:37:58] [Headless] WebUI running at http://192.168.1.160:3000
[2026-03-08 18:37:58] [Headless] Event forwarding configured for WebUI
[2026-03-08 18:37:58] [Headless] Polling: active=3s, inactive=3s
[2026-03-08 18:37:58] [Headless] Headless mode ready!

I tried using flashprint 5, however, and It had no trouble whatsoever. It simply uploaded and began printing.

[GhostTypes]

From the logs I can see that it's not getting a firmware version from your printer anymore, but the "authentication" process (M601) is still working fine

sendCommand: ~M602
CheckSocket()
sendCommand: ~M601 S1  <--- Authentication 
CheckSocket()    <---- All good
sendCommand: ~M115    <--- Requesting "printer info" (name/model. firmware version, etc)
CheckSocket()
PrinterInfo replay has null firmware version  <--- API is not able to parse the response from your printer
(Legacy API) Failed to get printer info, aborting.

I can make a script you can run to dump the "raw" response for this command and other so I can see what's changed and update my API.

Did you update the printer's firmware recently?

[GhostTypes]

Hey — I made a quick diagnostic script you can run to dump the raw TCP responses from your printer. This will show me exactly what your 3C is sending back for M115 so I can fix the parser.

How to run:

1. Make sure Python 3 is installed
2. Save the script below as flashforge_diag.py
3. Run it: python flashforge_diag.py
4. It will try to auto-discover your printer on the network. If that doesn't work, it'll ask you to enter the IP manually (you mentioned 192.168.1.235)
5. Paste the full output here as a reply

The script connects, sends M601/M115/M119/M105/M27/M114/M602 and dumps the raw text + hex for each response. Read-only, doesn't change anything on the printer.

flashforge_diag.py (click to expand)

#!/usr/bin/env python3
"""
FlashForge Printer Diagnostic Tool
Discovers printers on the network and dumps raw TCP command responses.
Useful for debugging parser issues with different firmware versions.
"""

import socket
import struct
import sys
import time

DISCOVERY_TIMEOUT = 5
TCP_PORT = 8899
TCP_TIMEOUT = 5

DIAG_COMMANDS = [
    ("M601 S1", "Session Init"),
    ("M115", "Printer Info"),
    ("M119", "Endstop / Machine Status"),
    ("M105", "Temperatures"),
    ("M27", "Print Status"),
    ("M114", "Position"),
    ("M602", "Session Release"),
]


def discover_printers():
    print("=" * 60)
    print("  FlashForge Printer Discovery")
    print("=" * 60)
    print()

    targets = [
        ("225.0.0.9", 19000, "Modern Multicast"),
        ("255.255.255.255", 48899, "Modern Broadcast"),
        ("225.0.0.9", 8899, "Legacy Multicast"),
    ]

    found = {}
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    sock.settimeout(DISCOVERY_TIMEOUT)

    try:
        sock.bind(("", 0))
        try:
            mreq = struct.pack("4s4s", socket.inet_aton("225.0.0.9"), socket.inet_aton("0.0.0.0"))
            sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)
        except OSError:
            pass

        probe = b"\x00"
        for addr, port, label in targets:
            try:
                sock.sendto(probe, (addr, port))
                print(f"  Sent probe: {label} ({addr}:{port})")
            except OSError as e:
                print(f"  Probe failed: {label} - {e}")

        print()
        print(f"  Listening for responses ({DISCOVERY_TIMEOUT}s)...")
        print()

        deadline = time.time() + DISCOVERY_TIMEOUT
        while time.time() < deadline:
            try:
                sock.settimeout(max(0.1, deadline - time.time()))
                data, (ip, port) = sock.recvfrom(1024)
            except socket.timeout:
                break
            if ip in found:
                continue

            pkt_len = len(data)
            name = serial = family = None

            if pkt_len >= 196:
                family = "Modern"
                name = data[0:132].split(b"\x00", 1)[0].decode("utf-8", errors="replace").strip()
                serial = data[0x92:0x92+130].split(b"\x00", 1)[0].decode("utf-8", errors="replace").strip()
            elif pkt_len >= 128:
                family = "Legacy"
                name = data[0:128].split(b"\x00", 1)[0].decode("utf-8", errors="replace").strip()
                serial = "(not in discovery packet)"

            if name:
                found[ip] = {"name": name, "serial": serial, "family": family, "packet_size": pkt_len}
                print(f"  FOUND: {name}")
                print(f"    IP: {ip} | Family: {family} ({pkt_len} bytes) | Serial: {serial}")
                print()
    finally:
        sock.close()
    return found


def send_command(sock, cmd):
    sock.sendall(f"~{cmd}\r\n".encode("utf-8"))
    response = b""
    sock.settimeout(TCP_TIMEOUT)
    try:
        while True:
            chunk = sock.recv(4096)
            if not chunk:
                break
            response += chunk
            text = response.decode("utf-8", errors="replace")
            if text.rstrip().endswith("ok") or "Control Success" in text or "Control Release" in text or "Error:" in text:
                break
    except socket.timeout:
        pass
    return response


def run_diagnostics(ip):
    print("=" * 60)
    print(f"  Running Diagnostics: {ip}:{TCP_PORT}")
    print("=" * 60)
    print()

    try:
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.settimeout(TCP_TIMEOUT)
        sock.connect((ip, TCP_PORT))
        print(f"  Connected to {ip}:{TCP_PORT}")
        print()
    except (socket.timeout, ConnectionRefusedError, OSError) as e:
        print(f"  ERROR: Could not connect to {ip}:{TCP_PORT} - {e}")
        return

    try:
        for cmd, label in DIAG_COMMANDS:
            print("-" * 60)
            print(f"  Command: ~{cmd}  ({label})")
            print("-" * 60)
            raw = send_command(sock, cmd)
            text = raw.decode("utf-8", errors="replace")
            print()
            print("  Raw response:")
            for line in text.splitlines():
                print(f"    | {line}")
            print()
            if len(raw) < 200:
                print(f"  Hex: {raw.hex()}")
                print()
            time.sleep(0.3)
    finally:
        try:
            send_command(sock, "M602")
        except Exception:
            pass
        sock.close()

    print("=" * 60)
    print("  Diagnostics complete!")
    print("=" * 60)


def main():
    print()
    print("  FlashForge Diagnostic Tool")
    print("  Discovers printers and dumps raw TCP responses")
    print()

    found = discover_printers()
    ip = None

    if found:
        printers = list(found.items())
        if len(printers) == 1:
            ip = printers[0][0]
            print(f"  Auto-selected: {printers[0][1]['name']} ({ip})")
            print()
        else:
            print("  Multiple printers found:")
            for i, (pip, info) in enumerate(printers, 1):
                print(f"    {i}. {info['name']} ({pip})")
            print()
            choice = input("  Select printer number (or enter IP manually): ").strip()
            if choice.isdigit() and 1 <= int(choice) <= len(printers):
                ip = printers[int(choice) - 1][0]
            else:
                ip = choice
    else:
        print("  No printers found via auto-discovery.")
        print()
        ip = input("  Enter printer IP address: ").strip()

    if not ip:
        print("  No IP provided. Exiting.")
        sys.exit(1)
    print()
    run_diagnostics(ip)


if __name__ == "__main__":
    main()

[crislobo-alt]

Thank you! I will run this as soon as i can

[crislobo-alt]

`
FlashForge Diagnostic Tool
Discovers printers and dumps raw TCP responses

============================================================
FlashForge Printer Discovery

Sent probe: Modern Multicast (225.0.0.9:19000)
Sent probe: Modern Broadcast (255.255.255.255:48899)
Sent probe: Legacy Multicast (225.0.0.9:8899)

Listening for responses (5s)...

No printers found via auto-discovery.

Enter printer IP address: 192.168.1.235

============================================================
Running Diagnostics: 192.168.1.235:8899

Connected to 192.168.1.235:8899

---

Command: ~M601 S1 (Session Init)

Raw response:
| CMD M601 Received.
| Control Success V2.1.
| ok

Hex: 434d44204d3630312052656365697665642e0d0a436f6e74726f6c20537563636573732056322e312e0d0a6f6b0d0a

---

Command: ~M115 (Printer Info)

Raw response:
| CMD M115 Received.
| Machine Type: FlashForge Adventurer III Pro
| Machine Name: CowaPrint
|
| Firmware: v2.1.2
| SN: SNCCCA95105901
| X: 150 Y: 150 Z: 150
| Tool Count: 1
| Mac Address:88:A9:A7:92:DE:72
|
| ok

---

Command: ~M119 (Endstop / Machine Status)

Raw response:
| CMD M119 Received.
| Endstop: X-max:0 Y-max:0 Z-max:0
| MachineStatus: READY
| MoveMode: READY
| Status: S:1 L:0 J:0 F:0
| LED: 1
| CurrentFile:
| ok

Hex: 434d44204d3131392052656365697665642e0d0a456e6473746f703a20582d6d61783a3020592d6d61783a30205a2d6d61783a300d0a4d616368696e655374617475733a2052454144590d0a4d6f76654d6f64653a2052454144590d0a5374617475733a20533a31204c3a30204a3a3020463a300d0a4c45443a20310d0a43757272656e7446696c653a200d0a6f6b0d0a

---

Command: ~M105 (Temperatures)

Raw response:
| CMD M105 Received.
| T0:23/0 B:11/0
| ok

Hex: 434d44204d3130352052656365697665642e0d0a54303a32332f3020423a31312f300d0a6f6b0d0a

---

Command: ~M27 (Print Status)

Raw response:
| CMD M27 Received.
| SD printing byte 0/100
| ok

Hex: 434d44204d32372052656365697665642e0d0a5344207072696e74696e67206279746520302f3130300d0a6f6b0d0a

---

Command: ~M114 (Position)

Raw response:
| CMD M114 Received.
| X:0 Y:0 Z:0 A:0 B:0
| ok

Hex: 434d44204d3131342052656365697665642e0d0a583a3020593a30205a3a3020413a3020423a300d0a6f6b0d0a

---

Command: ~M602 (Session Release)

Raw response:
| CMD M602 Received.
| Control Release.
| ok

Hex: 434d44204d3630322052656365697665642e0d0a436f6e74726f6c2052656c656173652e0d0a6f6b0d0a

============================================================
Diagnostics complete!
============================================================`

[GhostTypes]

Awesome thank you!!

Offhand it looks like all that was changed was an empty line (added) between the machine name and firmware version.

I'll have this fixed in the next alpha build which I'm preparing to release over this weekend👍🏼

The auto discovery should have worked, so if you don't mind I will send another script when I'm back on my PC to figure that out too.

I've only got one other semi active user with the Adv3 series, so any testing is greatly appreciated and helps improve compatibility for all users ❤️

[crislobo-alt]

Thank you so much for the help!

[GhostTypes]

This should be fixed in the new alpha build I just released

[GhostTypes]

Checking back in on this , were you able to get connected with the new alpha?

[crislobo-alt]

Sorry for the late reply, work ramped up... It works great! thank you for the help

[GhostTypes]

Sorry for the late reply, work ramped up... It works great! thank you for the help

No worries at all! Very happy to hear that got it working for you 😄

Feel free to reopen this (or a new issue) if you have any further troubles 👍