Remote buses¶

can-server shares the CAN interfaces of one computer, e.g. a Raspberry Pi with a CAN hat in a vehicle or on a test bench, with CANExplorer on other computers in the network. CANExplorer then works with the remote bus like with a local one: trace, recording, transmitting, diagnostics, simulation and tests.

Running the server¶

can-server is installed with CANExplorer (from source: uv run can-server). Name every bus to share and give its python-can interface, channel and bitrate:

can-server --bus vehicle=socketcan:can0:500000 --bus body=socketcan:can1:125000 --token "$(openssl rand -hex 16)"

Option	Description
`--bus NAME=INTERFACE:CHANNEL[:BITRATE[:DATA_BITRATE]]`	A bus to share (repeatable); a data bitrate enables CAN FD
`--host`	Address to listen on; default `0.0.0.0` (all networks)
`--port`	TCP port; default 8765
`--token`	Clients must present this token; also `CAN_SERVER_TOKEN`
`-v`	Log every client and bus event

A bus is opened when the first client connects to it and closed when the last one leaves. Several clients can use a bus at the same time; frames one of them sends are received by the others.

Security

Anyone who can reach the server and knows the token can read and send on the buses. Use a token, keep the server in a trusted network (or behind a VPN), and do not expose it to the internet. The connection is not encrypted; put a TLS proxy in front of the server and use wss:// URLs when it crosses untrusted networks.

With Docker, CAN_SERVER_TOKEN=… docker compose up -d can-server in the repository runs it as a service (see Building and testing). To start the server with the Pi without Docker, a systemd unit such as this one works:

[Unit]
Description=CAN server
After=network-online.target

[Service]
ExecStartPre=/usr/sbin/ip link set can0 up type can bitrate 500000
ExecStart=/home/pi/.local/bin/can-server --bus vehicle=socketcan:can0:500000
Environment=CAN_SERVER_TOKEN=change-me
Restart=on-failure

[Install]
WantedBy=multi-user.target

Connecting¶

In New connection, choose the interface RemoteBus and enter the channel HOST:PORT/BUS, with the token when the server needs one:

raspberrypi.local:8765/vehicle?token=change-me

Enter the bitrate of the remote bus too, for the bus load. Self-reception asks the server to echo the frames you send. Workspaces and recent connections remember remote connections like local ones.

When the connection to the server is lost, the connection shows the error and stops; Connect connects again. Timestamps are those of the server, so recordings have the timing of the remote bus, not of the network.

The remote bus is a python-can interface (canexplorer_remote), so scripts and can-test use it as well:

uv run can-test tests/ecu_tests.py --interface canexplorer_remote --channel "raspberrypi.local:8765/vehicle?token=change-me"

GET http://HOST:PORT/buses (with ?token=…) lists the buses of a server with their bitrates and clients.