micropython: Bugs and limitations of socket module

So I kept testing and it turns out that the problem is not the voltage or the socket.close() method.

There’s a problem with socket.recv(). After removing this from the code I was able to loop indefinetely without the module rebooting because it hangs, and the data gets correctly transmitted every time.

I do need to access the response from the server as it contains a few variables that the program inside the module uses.

I’ve read that other modules like ESP32 and ESP8266 have had this problem but they have been corrected so I don’t know why this happens with the latest version of micropython.

UPDATE:

I solved it by replacing response=s.recv(256) with

ready = select.select([s], [], [], 5)
if ready[0]:
     response=s.recv(256)

Now it loops forever without hanging 😃

The latest build produces this:

>>> s.setblocking(False)
>>> s.connect(('demo.traccar.org', 5055))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: [Errno 115] EINPROGRESS
>>> s.connect(('demo.traccar.org', 5055))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: 106

I do not know whether it is a fair result but, at least, it does not halt the module and is easy to implement.

I fixed one limiting case instead of the core problem which requires patching. Some of the underlying lwip exceptions are not written in errno: they are, for some reason, redirected to the platform error handler which displays an error in coolwatcher and halts the module. I will try to fix it.

I fixed this:

1. When s.connect called twice OSError(EISCONN) is raised
2. When calling s.recv on empty socket OSError(ENOTCONN) is raised (on ESP8266 it’s OSError(0))

Socket errors can be traced in cooltools. I was not able to reproduce the timeout problem: please provide a minimal working example.