LINUX

How To Use SocketCAN With The Command-Line In Linux

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Overview

This tutorial shows you how to manipulate SocketCAN interfaces using the Linux command-line. This includes finding out what SocketCAN interfaces are available, printing detailed info about them, and then sending/receiving data.

Icon for SocketCAN. Image from https://github.com/linux-can/can-utils.

Icon for SocketCAN. Image from https://github.com/linux-can/can-utils.

What Types of CAN Interfaces Are There?

SocketCAN provides the following types of CAN interfaces:

  1. Native interfaces. These are CAN interfaces associated with real hardware (such as a USB-to-CAN adapter). They are named canX , e.g. can0, can1, …
  2. Virtual interfaces. These are CAN interfaces that are not associated with any real hardware. They are named vcanX, e.g. vcan0, vcan1, …
  3. SLCAN based interfaces. SLCAN interfaces provide a serial interface. They are named slcanX, e.g. slcan0, slcan1, e.t.c

Investigating SocketCAN Interfaces

First off, you want to print all the available ip interfaces and see if you have some can interfaces. This uses the iproute2 suite of tools:

~$ ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
    link/ether 00:0c:29:35:8c:af brd ff:ff:ff:ff:ff:ff
3: can0: <NOARP,ECHO> mtu 16 qdisc noop state DOWN mode DEFAULT group default qlen 10
    link/can 

The last interface listed is can0. This is a SocketCAN interface!

Native CAN devices that support SocketCAN can be seen using the iproute2 suite of tools. For example:

~$ ip addr ls dev can0
3: can0: <NOARP,ECHO> mtu 16 qdisc noop state DOWN group default qlen 10
    link/can

If you attempt it for a CAN device that does not exist:

~$ ip addr ls dev can1
Device "can1" does not exist.

An alternative way to investigate CAN interfaces is to use ifconfig <canx>:

~$ ifconfig can0
can0: flags=128<NOARP>  mtu 16
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 10  (UNSPEC)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Configuring And Enabling The SocketCAN Interface

Before we can enable the SocketCAN interface, we need to configure it:

~$ sudo ip link set can0 type can bitrate 500000
~$ sudo modprobe vcan
~$ sudo ip link add dev vcan0 type vcan

Enabling a specific SocketCAN interface is also called “bringing the interface up”. To bring the connection up:

~$ sudo ip link set up can0

Note 1: If you ever get the following error: RTNETLINK answers: Operation not permitted, try the command again with sudo.

Note 2: And if you get the error: RTNETLINK answers: Operation not supported then try run sudo modprobe can (or sudo modprobe vcan ) first.

Send/Receive Data On SocketCAN

If you then want to send/receive data on the CAN interface, you should install can-utils:

~$ sudo apt install can-utils

The repository for can-utils can be found at https://github.com/linux-can/can-utils.

To send data to the CAN bus, use the cansend utility:

~$ cansend can0 123#1122334455667788

The above command will send a CAN message on can0 with the identifier 0x123 and the data bytes [ 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88 ]. Values are always treated as hexadecimal.

To display a list of received messages on the bus in realtime, use the candump utility:

~$ candump can0

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