CAN bus (Controller Area Network) is a robust serial bus standard originally developed by Bosch in the 1980s for in-vehicle communication. It allows multiple electronic control units (ECUs) to share a single twisted-pair cable, with built-in error detection and message prioritisation. CAN bus is now the dominant communication standard inside vehicles and is widely used in industrial machinery, agricultural equipment, and building services.

In short: CAN bus operates at speeds from 125 kbps to 1 Mbps (standard CAN), with CAN FD (Flexible Data-Rate) extending data-phase rates substantially higher. Messages on a CAN bus are broadcast to all nodes; each node decides whether the message is relevant. There is no master, no addressing in the usual sense: messages are identified by their content, and bus arbitration is non-destructive, so the highest-priority message wins without retries. Higher-level protocols including CANopen (industrial automation), J1939 (heavy-duty vehicles and machinery), and OBD-II (passenger car diagnostics) all run over CAN bus.

For IoT, CAN bus is the entry point to vehicle and machinery data. A cellular router or gateway with a CAN interface can read engine, transmission, fuel, fault-code, and operational data from a vehicle or machine, repackage it as MQTT or HTTP, and forward it to a cloud platform. Common applications include fleet telematics (driver behaviour, fuel consumption, fault prediction), construction and agricultural equipment monitoring (utilisation, location, maintenance triggers), and bus and rail telemetry.

Industrial routers with CAN interfaces include Teltonika models in the RUT and TRB families, alongside specialist gateways from other vendors. The choice between bare-CAN, CANopen, and J1939 support depends on the target equipment and the higher-level protocol it uses.