Architecture

canair never talks CAN directly — it reaches the bus through an adapter (a WiCAN dongle, or a generic ELM327 clone) over one of several explicitly-selected transports. Responses are parsed and decoded into named parameters using the active profile's definitions.

How it connects

flowchart LR
    subgraph host["Your computer — canair"]
        cli["canair CLI<br/>transport: wican-ws | slcan-tcp"]
        defs["Profile PID/DID defs<br/>+ captures"]
        isotp["client-side ISO-TP + UDS<br/>(pipelined; slcan-tcp only)"]
    end
    subgraph wican["WiCAN dongle — one protocol at a time"]
        ws["ELM327 WebSocket terminal"]
        slcan["SLCAN socket"]
    end
    subgraph car["Vehicle (OBD-II port)"]
        bus["CAN bus"]
        ecus["ECUs"]
    end
    cli -->|"wican-ws: ELM327 + UDS/KWP2000"| ws
    cli --> isotp
    isotp <-->|"slcan-tcp: raw CAN frames"| slcan
    ws <-->|"dongle does ISO-TP"| bus
    slcan <--> bus
    bus <--> ecus
    defs -.->|"decode responses"| cli

Transports

The device runs one protocol at a time — check with canair status.

• slcan-tcp (default) — a raw SLCAN frame stream over TCP. canair performs ISO-TP + UDS itself, pipelined across ECUs. Works on any WiCAN (Pro or classic) or gateway. Also powers canair sniff.
• wican-ws (Pro only) — the WiCAN Pro's ELM327 emulation over a WebSocket; the dongle performs ISO-TP.
• elm327-tcp — a generic ELM327 adapter over a plain TCP socket: the $10 WiFi clones (Kiwi, vLinker, OBDLink, no-name dongles) and the ELM327-Emulator's -n mode. No WiCAN, no HTTP config API — just the ELM327 terminal on a TCP port (usually 35000); the dongle performs ISO-TP.

slcan-tcp is the canonical default because it runs on both WiCAN hardware variants. Select a transport with --transport or the config transport: block. The ELM327 transports (wican-ws, elm327-tcp) share one ELM327 protocol engine — only the byte channel (WebSocket vs. plain TCP) differs — so every command works identically over each.

WiCAN is recommended; third-party dongles are best-effort

The elm327-tcp transport lets you use any generic ELM327 clone, but the WiCAN is the best-tested adapter for this project and is recommended. Cheap clones vary in firmware quality, can't be guaranteed reliable, and are especially likely to fall short on newer vehicles that depend on long multi-frame ISO-TP payloads and extended (29-bit) addressing. See Connect your dongle.

Protocols

• UDS (ISO 14229) — the modern diagnostic protocol.
• KWP2000 (ISO 14230) — the older protocol some ECUs still speak.
• ISO-TP (ISO 15765-2) — multi-frame transport underneath both.
• SLCAN-over-TCP and ELM327 AT — the host↔dongle link.

Which ECUs speak which protocol is vehicle-specific — canair auto-selects UDS vs. KWP2000 per ECU based on the profile registry or an on-device probe. (On the bundled Ioniq, for example, the powertrain ECUs — BMS, VCU, MCU, OBC — are KWP2000 while body/comfort ECUs are UDS; another car may split differently.)

Two data domains

canair handles two parallel kinds of data:

• Diagnostics — request/response UDS/KWP2000 (mature: read/scan/dtc/…).
• Raw frames — passively-sniffed broadcast traffic no request elicits (canair sniff).

Both are first-class. The transport layer treats the WiCAN as a replaceable way to reach the bus — a generic ELM327 clone (elm327-tcp) already slots in behind the same interface, and a future SocketCAN or replay backend could too.