pt., 7 maj 2021 o 09:02 Patrick Menschel <menschel.p@xxxxxxxxx> napisał(a): > > Am 06.05.21 um 23:28 schrieb Bartosz Zdanowicz: > >> Can you create a candump log from vcan0 to see, what's going on the bus? > >> > > On RPI after first send I got > > pi@raspberrypi:~ $ candump can0 > > can0 002 [8] 10 09 41 41 41 41 41 41 > > > > After the second message I got mentioned OSError and there is no data > > on candump. Sending again I received next frame: > > pi@raspberrypi:~ $ candump can0 > > can0 002 [8] 10 09 41 41 41 41 41 41 > > can0 002 [8] 10 09 41 41 41 41 41 41 > > > > On my local PC where I get no system Error I got one frame per every send: > > bartosz ~/Work/DeltaThermal/can-isotp master candump vcan0 > > vcan0 002 [8] 10 09 41 41 41 41 41 41 > > vcan0 002 [8] 10 09 41 41 41 41 41 41 > > vcan0 002 [8] 10 09 41 41 41 41 41 41 > > vcan0 002 [8] 10 09 41 41 41 41 41 41 > > vcan0 002 [8] 10 09 41 41 41 41 41 41 > > vcan0 002 [8] 10 09 41 41 41 41 41 41 > >> > >> ... > >> So how is Python getting this information? > >> > > In general, that's the biggest issue for me. Because in my real > > application I'm using python select() and recv() on that socket. When > > this error is raised, my select() on socket deduce something is > > received and recv() function also throws an error. I just tried to get > > a minimal example that reproduces the issue which is above. In those > > cases I would expect timeout, not OSError. > > > As expected, timeout error on missing flow control. Since it's tx side > it just tells -ECOMM instead of -ETIMEDOUT . > > https://github.com/raspberrypi/linux/blob/rpi-5.10.y/net/can/isotp.c#L10 > https://github.com/raspberrypi/linux/blob/rpi-5.10.y/net/can/isotp.c#L755 > > Is there a specific reason why you use select.select() instead of > Socket.recv(timeout) / Socket.send() ? > > Best Regards, > Patrick I have a seperate thread that waits and process data, since I have multiple sockets opened I want to wait for any of them: while True: ready_sockets = select.select(self.sockets, [], [], self.timeout)[0] if not ready_sockets: logging.info("No data received") continue for socket in ready_sockets: self.process_data(socket=socket) In process_data I call: received = socket.recv() if received: #process data My main thread is sending data on those sockets: schedule.every(X).seconds.do(request_that_sends_using_socket.send(), socket=socket) So the flow is that my thread sends data to another device, and the processing thread is waiting for data. When I don't send any data I get only prints "No data received" which is expected cause no device is responding (no device is running). When I send data (no other device is running) I get an error on send AND my select() is finished with an error socket inserted to ready_sockets. That means I enter self.process_data() function with socket and also recv() fails. So it seems it's not only that OSError is raised but also that socket is somehow "invalid" because it triggers select() which should not be triggered (no data was received). I hope I described it clearly, if any more details are needed I'll try to provide. Best Regards, Bartosz Zdanowicz
