python - Strange behaviour of my tcp socket connection(get wrong data after a some time)

Question

I have a function getData which I want to run continuously in a while True loop. I don't think something is wrong with the code, but I'm posting a snippet down below. When I run the code I have following strange behavior:

I get the correct Data but only for a certain time. For example I get the following dict:

{var1: 1290.0, var2: 100000.0, ....}

and after the Time where everything works correct there will be an Output as for example:

{var2: 12e-39, var2:-1213141412343, ...}

The lists I named #listofxy contains just the names of the parameters e.g

['ControlUnit/1', 'Calc_time(ms)', 'Time', ...]

or for the dtypes

['Int', 'Float', ...]

#Datapoints is the number of bytes I have to request to get for every variable one value(one package)

The server just sends raw data with a rate of 8000 packages per second(float or Int belongs to the Variable and is decaled in #listofdtypes). Every package has one value for every variable. My PC has a ethernet connection with the server.

So I do not think something is wrong with the server, because it gives me correct data till a certain time. And if something would be wrong with my data acquisition/code there should be an error much earlier and the error is not at the same time on every run. Also I don't think there is a bitshift, because I use a TCP-protocol which should guarantee this.

I also tested the programm on my laptop and had the same problem. Also an colleague has a programm to get data from my server and runs his programm on linux and he has not that issue. Meanwhile, I think there is something strange with windows(haven't tested it yet on a linux machine), but I don't really have a clue. Does someone have an idea why this could happen??

    def getData(self):

    dataB = b''
    self.vari = {key: [] for key in #listofNames}
    data = {key: [] for key in #listofNames2}

    # get requested number of data bytes
    dataB = dataB + self.sock_data.recv(#Datapoints)

    while len(dataB) != #requestedLenght:
        # check if requested number of data bytes and actual number of data bytes are the same
        dataB = dataB + self.sock_data.recv(1)

    dt_list = list((x, '<i4' if x == 'Int' else '<f4') for x in #listofdtypes)

    for i in range(0, #Datapoints):
        for j in range(0, len(#listofNames)):

    """
    some code to decode the bytes with a numpy.frombuffer function
    """

    for j in range(0, len(#listofNames)):
        data[#listofNames[j] = self.vari[#listofNames[j]]

    return data

question from:https://stackoverflow.com/questions/66068468/strange-behaviour-of-my-tcp-socket-connectionget-wrong-data-after-a-some-time

Answer 1

Waitting for answers