uSockRead should return if a socket is closed by remote

[arnoutdekimo]

Hi,

Just a comment on the workings of the function uSockRead.
If we set a read timeout of 10s (uSockOptionSet(sock, U_SOCK_OPT_LEVEL_SOCK, U_SOCK_OPT_RCVTIMEO), and poll uSockRead in a loop, we expected indeed after 10s of no data received, that the functions returns.

However, if the socket is closed within that time, the module does report this:

0:00:37:859 - OK
0:00:37:859 -
0:00:37:915 - +UUSOCL: 0
0:00:37:915 -
0:00:37:915 - OK
0:00:37:916 -
0:00:37:916 - +UUSOCL: 0
0:00:37:985 - AT+USORD=0,0
0:00:38:036 -
0:00:38:073 - +CME ERROR: Operation not allowed
0:00:38:074 -
0:00:38:074 - AT+USORD=0,0
0:00:38:191 -
0:00:38:231 - +CME ERROR: Operation not allowed
0:00:38:232 -
0:00:38:232 - AT+USORD=0,0
0:00:38:349 -
0:00:38:389 - +CME ERROR: Operation not allowed
0:00:38:390 -
0:00:38:390 - AT+USORD=0,0
0:00:38:507 -

But ubxlib does not use this information and keeps blocking for the timeout setting. (loop in receive function)

Ideally, a posix socket would directly return in this case, indicating that the connection has closed.

It's possible to work around this behavior, but just letting it know that it is unexpected.

[RobMeades]

Yes, I've wondered about capturing this and reporting it somehow, I will add it to the TODO list.

[arnoutdekimo]

(FYI, my current workaround is using small socket timeouts (using my own big one externally) + uSockRegisterCallbackClosed, and letting it set a boolean, so I can check after uSockRead returns -1 whether the socket is still alive or not. )

[RobMeades]

Hi Arnout: I've pushed a preview branch of the change here 4d29ef0. Is that the kind of change you were expecting? If so I'll push it to master here (then delete the preview branch).

[arnoutdekimo]

Hi, yup, sounds like what was missing, thanks!

[RobMeades]

The fix is now pushed to master here in commit c315b4f; I will delete the preview branch.