Fix reading from socket

[gerw]

Sometimes self._socket.recv returns fewer bytes than requested (for me, this happens sometimes over VPN). The current try-check in read_* is not helpful, since it just skews up the readings, e.g., if we only get 2 bytes for parameter 1, the remaining 2 bytes are then feed into parameter 2 and so on...

The current fix assures that the correct amount of bytes is read by introducing a new function _read_bytes().

[github-actions[bot]]

Coverage Report

File	Stmts	Miss	Cover	Missing
luxtronik
__init__.py	184	133	28%	39–51, 73–77, 80, 84–89, 93–97, 108–111, 119–121, 128–130, 137–139, 146–148, 157, 165–167, 170–173, 176–179, 182–198, 201–211, 214–226, 229–239, 243–245, 249–265, 269–270, 274–275, 286–288, 291, 294, 297, 300, 303–306, 309–312
__main__.py	21	21	0%	3–49
datatypes.py	275	1	99%	82
discover.py	40	34	15%	21–69
luxtronik/scripts
dump_changes.py	43	43	0%	7–85
dump_luxtronik.py	26	26	0%	6–52
TOTAL	675	258	62%

Tests	Skipped	Failures	Errors	Time
122	0 :zzz:	0 :x:	0 :fire:	0.762s :stopwatch:

[kbabioch]

What will happen if we request to read more data that is provided by the socket? Can thete be any kind of dead lock in this way?

[gerw]

Good point. I think one should check that at least one byte is returned, see https://docs.python.org/3/library/socket.html#socket.socket.recv.

In case nothing is returned by recv, the connection is lost. What to do in this case? Raise some error? Which one?