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.. _socketcand_doc:
socketcand Interface
====================
`Socketcand <https://github.com/linux-can/socketcand>`__ is part of the
`Linux-CAN <https://github.com/linux-can>`__ project, providing a
Network-to-CAN bridge as a Linux damon. It implements a specific
`TCP/IP based communication protocol <https://github.com/linux-can/socketcand/blob/master/doc/protocol.md>`__
to transfer CAN frames and control commands.
The main advantage compared to UDP-based protocols (e.g. virtual interface)
is, that TCP guarantees delivery and that the message order is kept.
Here is a small example dumping all can messages received by a socketcand
daemon running on a remote Raspberry Pi:
.. code-block:: python
import can
bus = can.interface.Bus(interface='socketcand', host="10.0.16.15", port=29536, channel="can0")
# loop until Ctrl-C
try:
while True:
msg = bus.recv()
print(msg)
except KeyboardInterrupt:
pass
The output may look like this::
Timestamp: 1637791111.209224 ID: 000006fd X Rx DLC: 8 c4 10 e3 2d 96 ff 25 6b
Timestamp: 1637791111.233951 ID: 000001ad X Rx DLC: 4 4d 47 c7 64
Timestamp: 1637791111.409415 ID: 000005f7 X Rx DLC: 8 86 de e6 0f 42 55 5d 39
Timestamp: 1637791111.434377 ID: 00000665 X Rx DLC: 8 97 96 51 0f 23 25 fc 28
Timestamp: 1637791111.609763 ID: 0000031d X Rx DLC: 8 16 27 d8 3d fe d8 31 24
Timestamp: 1637791111.634630 ID: 00000587 X Rx DLC: 8 4e 06 85 23 6f 81 2b 65
This interface also supports :meth:`~can.detect_available_configs`.
.. code-block:: python
import can
import can.interfaces.socketcand
cfg = can.interfaces.socketcand._detect_available_configs()
if cfg:
bus = can.Bus(**cfg[0])
The socketcand daemon broadcasts UDP beacons every 3 seconds. The default
detection method waits for slightly more than 3 seconds to receive the beacon
packet. If you want to increase the timeout, you can use
:meth:`can.interfaces.socketcand.detect_beacon` directly. Below is an example
which detects the beacon and uses the configuration to create a socketcand bus.
.. code-block:: python
import can
import can.interfaces.socketcand
cfg = can.interfaces.socketcand.detect_beacon(6000)
if cfg:
bus = can.Bus(**cfg[0])
Bus
---
.. autoclass:: can.interfaces.socketcand.SocketCanDaemonBus
:show-inheritance:
:member-order: bysource
:members:
.. autofunction:: can.interfaces.socketcand.detect_beacon
Socketcand Quickstart
---------------------
The following section will show how to get the stuff installed on a Raspberry Pi with a MCP2515-based
CAN interface, e.g. available from `Waveshare <https://www.waveshare.com/rs485-can-hat.htm>`__.
However, it will also work with any other socketcan device.
Install CAN Interface for a MCP2515 based interface on a Raspberry Pi
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Add the following lines to ``/boot/config.txt``.
Please take care on the frequency of the crystal on your MCP2515 board::
dtparam=spi=on
dtoverlay=mcp2515-can0,oscillator=12000000,interrupt=25,spimaxfrequency=1000000
Reboot after ``/boot/config.txt`` has been modified.
Enable socketcan for can0
~~~~~~~~~~~~~~~~~~~~~~~~~
Create config file for systemd-networkd to start the socketcan interface automatically:
.. code-block:: bash
cat >/etc/systemd/network/80-can.network <<'EOT'
[Match]
Name=can0
[CAN]
BitRate=250K
RestartSec=100ms
EOT
Enable ``systemd-networkd`` on reboot and start it immediately (if it was not already startet):
.. code-block:: bash
sudo systemctl enable systemd-networkd
sudo systemctl start systemd-networkd
Build socketcand from source
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. code-block:: bash
# autoconf is needed to build socketcand
sudo apt-get install -y autoconf
# clone & build sources
git clone https://github.com/linux-can/socketcand.git
cd socketcand
./autogen.sh
./configure
make
Install socketcand
~~~~~~~~~~~~~~~~~~
.. code-block:: bash
make install
Run socketcand
~~~~~~~~~~~~~~
.. code-block:: bash
./socketcand -v -i can0
During start, socketcand will prompt its IP address and port it listens to::
Verbose output activated
Using network interface 'eth0'
Listen adress is 10.0.16.15
Broadcast adress is 10.0.255.255
creating broadcast thread...
binding socket to 10.0.16.15:29536
|
