Most MILCAN A deployments assume dedicated CAN controller hardware and a vendor-supplied stack bolted onto it. milcan-daemon is different: it is pure userspace software. It opens a standard Linux SocketCAN interface a real CAN adapter, or a virtual vcan0 interface for development and CI and implements the full MILCAN A data-link and application-layer behaviour itself, in C++20 on top of Qt6.

Because it's software, it drops onto anything: a vehicle compute unit, a test bench, a CI runner, or a developer's laptop with vcan0 — with the same binary and the same behaviour every time.

• ✅ Pure userspace daemon — no kernel module, no vendor hardware, no proprietary SDK
• ✅ Full MILCAN A protocol (MWG-MILA-001 Rev 3): 29-bit identifier decode/encode, message classification, priority-based bus access
• ✅ Compulsory system-mode state machine (Pre-Operational / Operational / System Configuration)
• ✅ Sync Master election with source-address priority arbitration
• ✅ 8-priority-ring transmit queue with "mortal"/TTL frame expiry and the mandatory max-one-per-PTU rule
• ✅ Multi-frame transport with CRC-16/CCITT for payloads beyond 8 bytes
• ✅ Config-driven semantic decoding — name your own (primaryType, subType) message sets in JSON, no code changes
• ✅ Local IPC surface (Unix domain socket, newline-delimited JSON) so any process — DDS bridge, logger, dashboard — can consume decoded traffic
• ✅ Three purpose-built CLI tools, packaged in a single Debian package with the daemon
• ✅ Runs identically on real CAN hardware or vcan0 — same binary, same behaviour

MILCAN A for Linux doesn't stop at the daemon — it ships a complete, protocol-aware toolset so you never need to hand-roll cansend invocations or decode 29-bit identifiers by hand.

🔍 milcan-dump — see every frame, decoded

A MILCAN-aware candump. Every frame is shown with its priority, protocol bit, primary/sub-type, source address, and classified message type (SyncFrame, Alive, StatusCommand, ...) — plus, with a message-set config, named parameter values decoded to engineering units.

milcan-dump -i vcan0 -c /etc/milcan/milcan-config.json

vcan0     0F730214  [0]                            pri=3 milcan primary=0x73 sub=0x02 src=0x14  class=Request
vcan0     06710114  [2]  0C 01                     pri=1 milcan primary=0x71 sub=0x01 src=0x14  class=StatusCommand
vcan0     06710214  [2]  0C 01                     pri=1 milcan primary=0x71 sub=0x02 src=0x14  class=StatusCommand
vcan0     0A720214  [2]  0C 01                     pri=2 milcan primary=0x72 sub=0x02 src=0x14  class=StatusCommand
vcan0     0F730214  [0]                            pri=3 milcan primary=0x73 sub=0x02 src=0x14  class=Request
vcan0     1E310014  [2]  48 49                     pri=7 milcan primary=0x31 sub=0x00 src=0x14  class=NonOperational
vcan0     1A620C0C  [1]  01                        pri=6 milcan primary=0x62 sub=0x0C src=0x0C  class=Alive

A real capture of 14 simulated vehicle signals across all 7 priority rings (engine RPM, wheel speed, brake pressure, GPS, diagnostics, and more) — see the bus-saturation-demo walkthrough for the source of this traffic. Note the mix of message classes: Request (no payload, bit set), StatusCommand (periodic signal values), and NonOperational (broadcast beacon) all decoded correctly, at their own priority.

A canplay-alike that replays a candump -l format log back onto SocketCAN, respecting recorded relative timing, with speed control and loop mode — ideal for regression tests and bench demos without a live bus.

milcan-play --interface=vcan0 --loop capture.log

📤 milcan-send — spec-correct frames, no hand-computed IDs

A cansend replacement purpose-built for MILCAN A: every message class the spec defines — Sync Frame, Enter/Exit Configuration Mode, Alive, Request, Non-operational broadcast, Status/Command — is a named subcommand. You never need to hand-compute a 29-bit identifier again.

milcan-send -i vcan0 enter-config --src 5
milcan-send -i vcan0 sync --slot 0
milcan-send -i vcan0 alive --node 7

Every piece of the stack — reading, classifying, sequencing, and writing frames — is a plain C++20/Qt6 object running in a normal Linux process. There is no firmware to flash and no kernel driver beyond the standard SocketCAN stack already in your kernel.

System Mode State Machine

MILCAN A mandates a system-mode state machine (§4.2, Fig 4-4) that every node must implement correctly — milcan-daemon implements it exactly as specified:

Sync Master Election

Nodes marked as potential Sync Masters arbitrate for the role using
source-address priority (Fig 4-3):

# Create a virtual CAN interface — no hardware required
sudo modprobe vcan
sudo ip link add dev vcan0 type vcan
sudo ip link set up vcan0

# Install the daemon and all three tools (single package)
sudo apt-get install milcan

# Start the daemon
milcan-daemon --interface=vcan0 --config=/etc/milcan/milcan-config.json

# In another terminal, watch decoded traffic
milcan-dump -i vcan0

# In a third terminal, inject a Sync Frame
milcan-send -i vcan0 sync --slot 0

Full walkthrough: First-Time Setup

Use Cases

🎖️ Vehicle Subsystem Integration Testing

Bring up and exercise a full MILCAN A node/device on a bench or in CI using only vcan0 — no vehicle bus, no adapter, no vendor tooling required.

🧪 Protocol Conformance Verification

Use milcan-send to exercise every message class a real ECU must handle, and milcan-dump to verify the responses, without writing a single line of bespoke test code.

📼 Regression and Demo Capture

Capture representative bus traffic once with milcan-dump -w, then replay it deterministically with milcan-play for demos, regression suites, or offline analysis.

🔌 Bridging to Other Systems

Consume decoded MILCAN A traffic from the local IPC surface in any language that can speak newline-delimited JSON over a Unix domain socket — logging, dashboards, or a bridge into another bus or middleware.