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Discovery Protocol
FlashForge printers use UDP-based discovery protocols to announce their presence on the network. A client implementation must handle both modern and legacy protocols to support the full printer fleet.
| Family | Protocol Type | Ports | Packet Size | Key Identifier |
|---|---|---|---|---|
| Modern (5M / 5M Pro / AD5X / Creator 5) | UDP Broadcast & Multicast | 19000 (Multi), 48899 (Broad) | 276-280 bytes | Serial Number (Offset 0x92) |
| Legacy (A3 / A4 Pro) | UDP Multicast | 8899 | 140 bytes | Machine Name (Offset 0x00) |
Multicast Group: 225.0.0.9
Modern printers listen on both multicast and broadcast addresses:
| Type | Address | Port |
|---|---|---|
| Multicast | 225.0.0.9 | 19000 |
| Broadcast | 255.255.255.255 | 48899 |
Probe: Send any UDP packet (payload ignored) to either address.
Response: Fixed-size binary packet. The size depends on the firmware generation:
| Firmware | Packet Size |
|---|---|
| 3.x (5M / 5M Pro / AD5X) | 276 bytes (0x114) |
| 5.x (5M / 5M Pro) | 280 bytes (0x118) |
| Creator 5 / Creator 5 Pro (all firmware) | 276 bytes (0x114) |
Firmware 5.x appends four trailing bytes after the Serial Number field. Check the length as "276 or more". Never check for one exact size. Creator 5 and Creator 5 Pro always send 276 bytes.
Total Size: 276 bytes (0x114) on firmware 3.x. 280 bytes (0x118) on firmware 5.x. (Big Endian)
| Offset | Size | Type | Description |
|---|---|---|---|
| 0x00 | 128 | char[] | Machine Name (null-terminated) |
| 0x80 | 4 | bytes | Padding (zeroed) |
| 0x84 | 2 | uint16 | Command Port (TCP), typically 8899. Creator 5 and Creator 5 Pro report 8899 here. They run no TCP server. Use the HTTP/Event port instead |
| 0x86 | 2 | uint16 | VID - typically 0x2B71 |
| 0x88 | 2 | uint16 | PID - model specific, see Printer PIDs |
| 0x8A | 2 | uint16 | Status Code - 0=Ready, 1=Busy, 2=Error |
| 0x8C | 2 | uint16 | Product Type (e.g., 0x5A02). Every 5M-platform model uses this value, including AD5X and Creator 5. Use the PID at 0x88 to tell the models apart |
| 0x8E | 2 | uint16 | HTTP/Event Port - typically 8898 |
| 0x90 | 2 | bytes | Reserved |
| 0x92 | 128 | char[] | Serial Number (null-terminated) |
| 0x112 | 2+ | bytes | Firmware 3.x and Creator 5: padding. Firmware 5.x (5M / 5M Pro): product type repeated (2 bytes), fixed 0x01 (1 byte), padding |
The status code at 0x8A shows basic printer state: 0 = Ready, 1 = Busy, 2 = Error. The printer updates this value only in a new discovery packet. This is a snapshot, not a live push. Poll /detail status for the current state.
If a packet is 196 bytes (0xC4) or longer, parse it as the modern protocol.
Legacy printers listen on multicast only:
| Type | Address | Port |
|---|---|---|
| Multicast | 225.0.0.9 | 8899 |
Probe: Send any UDP packet to the multicast address.
Response: Fixed-size binary packet (140 bytes).
Total Size: 140 bytes (Big Endian)
| Offset | Size | Type | Description |
|---|---|---|---|
| 0x00 | 128 | char[] | Machine Name (null-terminated) |
| 0x80 | 4 | bytes | Padding (zeroed) |
| 0x84 | 2 | uint16 | Command Port (TCP) - typically 8899 |
| 0x86 | 2 | uint16 | Vendor ID - typically 0x2B71 |
| 0x88 | 2 | uint16 | Product ID - e.g., 0x001D |
| 0x8A | 2 | uint16 | Status Code (0=Ready, 1=Busy, 2=Error) |
If a packet is exactly 140 bytes, parse it as the legacy protocol.
The legacy packet does not contain the Serial Number. To retrieve the SN for unique identification, you must:
- Connect via TCP to port 8899
- Send
~M115 - Parse the Serial Number from the response
To auto-discover any FlashForge printer:
Bind a UDP socket capable of receiving from multiple interfaces.
Send discovery probes to all known addresses:
225.0.0.9:19000 (Modern Multicast)
255.255.255.255:48899 (Modern Broadcast)
225.0.0.9:8899 (Legacy Multicast)
Parse responses based on packet length:
Packet Length >= 196 --> Modern Protocol
Packet Length == 140 --> Legacy Protocol
Modern packets are 276 bytes on firmware 3.x and 280 bytes on firmware 5.x. Accept both lengths.
For legacy printers, initiate a TCP connection to retrieve the serial number.
| Field | Modern (276 bytes) | Legacy (140 bytes) |
|---|---|---|
| Machine Name | Yes (offset 0x00, 128B + 4B pad) | Yes (offset 0x00, 128B + 4B pad) |
| Serial Number | Yes (offset 0x92, 128B + 2B pad) | No (requires TCP) |
| Command Port | Yes (offset 0x84) | Yes (offset 0x84) |
| HTTP/Event Port | Yes (offset 0x8E) | No |
| Status Code | Yes (offset 0x8A) | Yes (offset 0x8A) |
| VID/PID | Yes (offsets 0x86, 0x88) | Yes (offsets 0x86, 0x88) |
| Product Type | Yes (offset 0x8C) | No |
- Verify the printer is powered on and connected to the network
- Check that firewall settings allow UDP traffic on the discovery ports
- Ensure your computer is on the same network segment as the printer
- Try direct IP connection if discovery fails
A single printer may respond to multiple probe addresses. Use the IP address or serial number to deduplicate responses.
For legacy printers, always fetch the serial number via TCP ~M115 before caching or displaying printer details. The machine name alone may not be unique across multiple printers.