python-can-isotp

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A standard python socket would encounter a socket.timeout Exception on recv() if no data came in. The can-isotp package, on the other hand, catches the exception and converts it into a return None.

I think this is wrong for several reasons:

1. It deviates from the programmer's expectations that a can-isotp socket behaves like a regular python socket.
2. The can-isotp package may not know if a timeout is an error or normal behavior. It is up to application code to determine.
3. It obscures that the application may be waiting for IO before reaching a timeout.
4. Code that expects to catch a timeout exception may end up generating a TypeError as it works with the None object.

Proposal:

When istop.socket.recv() times out, the socket.timeout error should either be passed down, or converted and re-raised explicitly as a TimeoutError().

Example

sock = isotp.socket()
sock.set_opts(txpad=0xcc)
sock.bind("can0", isotp.Address(txid=0x7e0, rxid=0x7e8))

bogus_msg = bytes([0xde, 0xad, 0xc0, 0xff, 0xee])
answer sock.send(bogus_msg)
try:
	answer = sock.recv()
except socket.error as err:
	# EXPECTATION: we hit this handler
	return

# REALITY: We get a None object when we expect actual data
# The line below will explode with an isotp socket
print(len(answer))

Indeed. I think you are right. i will have to double check not to break anything that is based on that behaviour.

Quick update. I'm starting to look at redesigning how reception is done. This will be fixed. There will be a breaking change, causing v2.0

This has been corrected in the newly created v2.x branch. Closing the issue.

thank you