FlowControl frame address tx_id vs. rx_id - 8? about can-isotp HOT 2 CLOSED

Thank you SO much for that clarification! I really appreciate you helping me learn and understand this material!

from can-isotp.

I have to create 2 sockets, one to send the request, and one to listen for the response. This doesn't seem to me like normal use,

It is ;-)

The difference is: With the so called 'functional addressing' you (as a diag tester) send a broadcast command to all ECUs. As this is a broadcast ( 1-to-n) it has to fit in ONE CAN frame (no segmentation, no FC frame). In your example you send this 'functional broadcast' with CAN ID 0x7DF.

After sending that message the ECUs start sending on a 'normal' point-to-point (1-to-1) ISO-TP channel.

And this channel needs two CAN ID, e.g. 0x7E8 and 0x7E0.

Even if it sounds strange: For your use-case you need to open eight ISO-TP sockets that virtually 'establish' the 1-to-1 ISO-TP channels.

Then you send the functional command with CAN ID 0x7DF and you can see the responses arriving on these sockets (you can use select() to read from multiple sockets at a time).

I assume establishing the Linux isotp socket after getting the first answer (like in the panda code) would be too late (as the isotp state machine then would miss the first CAN frame).

from can-isotp.