8000 socketcand Backend for python-can (#1140) · hardbyte/python-can@acc2ebd · GitHub
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domologictelkamp
domologic
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socketcand Backend for python-can (#1140)
* merge most recent version of socketcand-interface branch * don't change loggine level * do not request python 3.7 * parse < hi > & < ok > messages * Initial upload: Doc for interfaces/socketcand * Python code example was not displayed * indent issues * minor changes * code optimization as proposed by felix * Typo * Monor doc improvement * license information added * reformatted using https://black.vercel.app/ * license removed Co-authored-by: Gerrit Telkamp <g.telkamp@domologic.de>
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‎can/interfaces/__init__.py

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"gs_usb": ("can.interfaces.gs_usb", "GsUsbBus"),
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"nixnet": ("can.interfaces.nixnet", "NiXNETcanBus"),
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"neousys": ("can.interfaces.neousys", "NeousysBus"),
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"socketcand": ("can.interfaces.socketcand", "SocketCanDaemonBus"),
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}
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try:

‎can/interfaces/socketcand/__init__.py

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"""
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Interface to socketcand
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see https://github.com/linux-can/socketcand
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Copyright (C) 2021 DOMOLOGIC GmbH
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http://www.domologic.de
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"""
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from .socketcand import SocketCanDaemonBus

‎can/interfaces/socketcand/socketcand.py

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"""
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Interface to socketcand
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see https://github.com/linux-can/socketcand
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Authors: Marvin Seiler, Gerrit Telkamp
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Copyright (C) 2021 DOMOLOGIC GmbH
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http://www.domologic.de
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"""
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import can
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import socket
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import select
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import logging
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import time
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import traceback
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from collections import deque
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log = logging.getLogger(__name__)
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def convert_ascii_message_to_can_message(ascii_msg: str) -> can.Message:
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if not ascii_msg.startswith("< frame ") or not ascii_msg.endswith(" >"):
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log.warning(f"Could not parse ascii message: {ascii_msg}")
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return None
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else:
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# frame_string = ascii_msg.removeprefix("< frame ").removesuffix(" >")
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frame_string = ascii_msg[8:-2]
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parts = frame_string.split(" ", 3)
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can_id, timestamp = int(parts[0], 16), float(parts[1])
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data = bytearray.fromhex(parts[2])
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can_dlc = len(data)
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can_message = can.Message(
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timestamp=timestamp, arbitration_id=can_id, data=data, dlc=can_dlc
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)
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return can_message
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def convert_can_message_to_ascii_message(can_message: can.Message) -> str:
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# Note: socketcan bus adds extended flag, remote_frame_flag & error_flag to id
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# not sure if that is necessary here
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can_id = can_message.arbitration_id
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# Note: seems like we cannot add CANFD_BRS (bitrate_switch) and CANFD_ESI (error_state_indicator) flags
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data = can_message.data
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length = can_message.dlc
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bytes_string = " ".join("{:x}".format(x) for x in data[0:length])
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return f"< send {can_id:X} {length:X} {bytes_string} >"
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def connect_to_server(s, host, port):
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timeout_ms = 10000
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now = time.time() * 1000
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end_time = now + timeout_ms
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while now < end_time:
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try:
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s.connect((host, port))
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return
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except Exception as e:
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log.warning(f"Failed to connect to server: {type(e)} Message: {e}")
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now = time.time() * 1000
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raise TimeoutError(
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f"connect_to_server: Failed to connect server for {timeout_ms} ms"
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)
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class SocketCanDaemonBus(can.BusABC):
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def __init__(self, channel, host, port, can_filters=None, **kwargs):
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self.__host = host
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self.__port = port
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self.__socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
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self.__message_buffer = deque()
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self.__receive_buffer = "" # i know string is not the most efficient here
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connect_to_server(self.__socket, self.__host, self.__port)
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self._expect_msg("< hi >")
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log.info(
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f"SocketCanDaemonBus: connected with address {self.__socket.getsockname()}"
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)
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self._tcp_send(f"< open {channel} >")
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self._expect_msg("< ok >")
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self._tcp_send(f"< rawmode >")
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self._expect_msg("< ok >")
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super().__init__(channel=channel, can_filters=can_filters)
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def _recv_internal(self, timeout):
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if len(self.__message_buffer) != 0:
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can_message = self.__message_buffer.popleft()
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return can_message, False
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try:
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# get all sockets that are ready (can be a list with a single value
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# being self.socket or an empty list if self.socket is not ready)
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ready_receive_sockets, _, _ = select.select(
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[self.__socket], [], [], timeout
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)
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except socket.error as exc:
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# something bad happened (e.g. the interface went down)
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log.error(f"Failed to receive: {exc}")
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raise can.CanError(f"Failed to receive: {exc}")
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try:
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if not ready_receive_sockets:
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# socket wasn't readable or timeout occurred
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log.debug("Socket not ready")
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return None, False
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ascii_msg = self.__socket.recv(1024).decode(
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"ascii"
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) # may contain multiple messages
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self.__receive_buffer += ascii_msg
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log.debug(f"Received Ascii Message: {ascii_msg}")
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buffer_view = self.__receive_buffer
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chars_processed_successfully = 0
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while True:
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if len(buffer_view) == 0:
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break
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start = buffer_view.find("<")
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if start == -1:
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log.warning(
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f"Bad data: No opening < found => discarding entire buffer '{buffer_view}'"
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)
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chars_processed_successfully = len(self.__receive_buffer)
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break
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end = buffer_view.find(">")
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if end == -1:
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log.warning("Got incomplete message => waiting for more data")
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if len(buffer_view) > 200:
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log.warning(
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"Incomplete message exceeds 200 chars => Discarding"
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)
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chars_processed_successfully = len(self.__receive_buffer)
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break
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chars_processed_successfully += end + 1
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single_message = buffer_view[start : end + 1]
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parsed_can_message = convert_ascii_message_to_can_message(
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single_message
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)
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if parsed_can_message is None:
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log.warning(f"Invalid Frame: {single_message}")
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else:
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self.__message_buffer.append(parsed_can_message)
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buffer_view = buffer_view[end + 1 :]
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self.__receive_buffer = self.__receive_buffer[
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chars_processed_successfully + 1 :
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]
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can_message = (
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None
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if len(self.__message_buffer) == 0
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else self.__message_buffer.popleft()
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)
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return can_message, False
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except Exception as exc:
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log.error(f"Failed to receive: {exc} {traceback.format_exc()}")
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raise can.CanError(f"Failed to receive: {exc} {traceback.format_exc()}")
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def _tcp_send(self, msg: str):
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log.debug(f"Sending TCP Message: '{msg}'")
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self.__socket.sendall(msg.encode("ascii"))
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def _expect_msg(self, msg):
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ascii_msg = self.__socket.recv(256).decode("ascii")
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if not ascii_msg == msg:
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raise can.CanError(f"{msg} message expected!")
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def send(self, msg, timeout=None):
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ascii_msg = convert_can_message_to_ascii_message(msg)
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self._tcp_send(ascii_msg)
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def shutdown(self):
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self.stop_all_periodic_tasks()
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self.__socket.close()

‎doc/interfaces/socketcand.rst

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

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