Dante Control Protocol Notes

All Dante control packets are UDP on port 4440.

Packet Header (10 bytes)

0x00: u8   magic        # 0x27=standard, 0x28=extended
0x01: u8   seq_lo
0x02: u16  length       # total packet length
0x04: u16  seq_id
0x06: u16  command
0x08: u16  status
0x0a: ...  args/data

All multi-byte fields are big-endian.

Commands

0x1000 - Channel Count Query

Response:

0x0c: u16  tx_count
0x0e: u16  rx_count

0x3000 - Subscription Query (Standard)

Works for multicast; may return empty for unicast.

Request args (6 bytes):

0x00: u16  0x0001
0x02: u16  page_num
0x04: u16  0x0000

Response record types (at 0x0e):

0x0006 = unicast
0x000e = multicast

0x3400 - Subscription Query (Extended)

Uses magic=0x28. Works for unicast flows.

Request args (24 bytes):

0x07: u8   0x01
0x08: u16  page_type    # 0x0001=first, 0x0003=subsequent
0x0a: u16  start_ch     # 1, 17, 33, 49, ...

0x3400 Response

0x00: [10] header
0x0a: [8]  extended_header
0x12: [32] offset_table     # 16 × u16 record offsets
0x32: ...  records + strings

Status (at 0x08):

0x8112 = has subscription data
0x0001 = empty page

Offset Table

16 entries at 0x12-0x31, each a u16 absolute offset to a record. Zero offset = no more records.

Subscription Record

Each record is 56+ bytes. The offset table points to record start.

record+0x00: [40] record_header
record+0x28: u16  0x0608          # marker
record+0x2a: u16  0x0000
record+0x2c: u16  tx_ch_offset    # absolute offset to TX channel name string
record+0x2e: u16  tx_dev_offset   # absolute offset to TX device name string
record+0x30: [4]  flags
record+0x34: u32  0x02020000      # string marker
record+0x38: ...  inline_strings  # (unreliable, use offsets above)

Subscription status:

Both offsets non-zero = subscribed
Both offsets zero = unsubscribed

String Table

Null-terminated strings referenced by absolute offset from packet start. Multiple records share strings (e.g., same device name).

Example: Page 2 Response (channels 17-32)

Offset table: 0050 0090 00d0 0110 0158 0194 01d8 021c 0258 ...

Record at 0x0050 (RX ch 17):
  0x0050+0x2c: 0032 0035
  String at 0x32: "01"       -> TX channel
  String at 0x35: "MICS-E"   -> TX device
  Result: MICS-E[01] -> ch17

Record at 0x0158 (RX ch 21):
  0x0158+0x2c: 0032 0148
  String at 0x32: "01"
  String at 0x148: "TX-QLAB-1"
  Result: TX-QLAB-1[01] -> ch21

Record at 0x01d8 (RX ch 23):
  0x01d8+0x2c: 01cc 01d1
  String at 0x1cc: "Left"
  String at 0x1d1: "BT"
  Result: BT[Left] -> ch23

Record at 0x0258 (RX ch 25):
  0x0258+0x2c: 0000 0000
  Result: UNSUBSCRIBED

Parsing Algorithm

Check magic=0x28, command=0x3400, status=0x8112
Read 16 offsets from 0x12-0x31
For each non-zero offset:
- Read u16 at offset+0x2c (tx_ch_offset)
- Read u16 at offset+0x2e (tx_dev_offset)
- If both zero: skip (unsubscribed)
- Else: read null-terminated strings at those offsets
- RX channel = page_start + record_index

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