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Porting Python2 to Python3 - Reading Bytes from a socket and using unpack() correctly

There is code here that I am trying to convert from Python2 to Python3. In this section of code, data is received from a socket. data is declared to be an empty string and then concatenated. This is an important Python2 to 3 distinction. In Python3, the 'received' variable is of type Bytes and thus needs to be converted to string first via the use of str(). However, str() needs an encoding parameter. What would the default one be for python 2? I've tried several different encodings (latin-1 and such) but they seem to not match up with a magic value that is defined here after being unpacked here
"\xffSMB seems to decode correctly while "\xfeSMB does not.
I have adjusted the non_polling_read function and the NetBIOSSessionPacket class as follows. Full modified source code available on GitHub.
def non_polling_read(self, read_length, timeout):
data = b''
bytes_left = read_length
while bytes_left > 0:
try:
ready, _, _ = select.select([self._sock.fileno()], [], [], timeout)
if not ready:
raise NetBIOSTimeout
received = self._sock.recv(bytes_left)
if len(received) == 0:
raise NetBIOSError('Error while reading from remote', ERRCLASS_OS, None)
data = data + received
bytes_left = read_length - len(data)
except select.error as ex:
if ex[0] != errno.EINTR and ex[0] != errno.EAGAIN:
raise NetBIOSError('Error occurs while reading from remote', ERRCLASS_OS, ex[0])
return data
class NetBIOSSessionPacket:
def __init__(self, data=0):
self.type = 0x0
self.flags = 0x0
self.length = 0x0
if data == 0:
self._trailer = ''
else:
try:
self.type = data[0]
if self.type == NETBIOS_SESSION_MESSAGE:
self.length = data[1] << 16 | (unpack('!H', data[2:4])[0])
else:
self.flags = data[1]
self.length = unpack('!H', data[2:4])[0]
self._trailer = data[4:]
except Exception as e:
import traceback
traceback.print_exc()
raise NetBIOSError('Wrong packet format ')
When I start the server and issue 'smbclient -L 127.0.0.1 -d 4' from the commandline, the server first creates a libs.nmb.NetBIOSTCPSession which appears to be working well. Once it tries to unwrap the libs.nmb.NetBIOSSessionPacket, it throws an exception.
Traceback (most recent call last):
File "/root/PycharmProjects/HoneySMB/libs/smbserver.py", line 3975, in processRequest
packet = smb.NewSMBPacket(data=data)
File "/root/PycharmProjects/HoneySMB/libs/smb.py", line 690, in __init__
Structure.__init__(self, **kargs)
File "/root/PycharmProjects/HoneySMB/libs/structure.py", line 77, in __init__
self.fromString(data)
File "/root/PycharmProjects/HoneySMB/libs/structure.py", line 144, in fromString
self[field[0]] = self.unpack(field[1], data[:size], dataClassOrCode = dataClassOrCode, field = field[0])
File "/root/PycharmProjects/HoneySMB/libs/structure.py", line 288, in unpack
raise Exception("Unpacked data doesn't match constant value %r should be %r" % (data, answer))
Exception: ("Unpacked data doesn't match constant value b'\\xffSMB' should be 'ÿSMB'", 'When unpacking field \'Signature | "ÿSMB | b\'\\xffSMBr\\x00\\x00\\x00\\x00\\x18C\\xc8\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\xfe\\xff\\x00\\x00\\x00\\x00\\x00\\xb1\\x00\\x02PC NETWORK PROGRAM 1.0\\x00\\x02MICROSOFT NETWORKS 1.03\\x00\\x02MICROSOFT NETWORKS 3.0\\x00\\x02LANMAN1.0\\x00\\x02LM1.2X002\\x00\\x02DOS LANMAN2.1\\x00\\x02LANMAN2.1\\x00\\x02Samba\\x00\\x02NT LANMAN 1.0\\x00\\x02NT LM 0.12\\x00\\x02SMB 2.002\\x00\\x02SMB 2.???\\x00\'[:4]\'')
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/root/PycharmProjects/HoneySMB/libs/smbserver.py", line 3597, in handle
resp = self.__SMB.processRequest(self.__connId, p.get_trailer())
File "/root/PycharmProjects/HoneySMB/libs/smbserver.py", line 3979, in processRequest
packet = smb2.SMB2Packet(data=data)
File "/root/PycharmProjects/HoneySMB/libs/smb3structs.py", line 435, in __init__
Structure.__init__(self,data)
File "/root/PycharmProjects/HoneySMB/libs/structure.py", line 77, in __init__
self.fromString(data)
File "/root/PycharmProjects/HoneySMB/libs/structure.py", line 144, in fromString
self[field[0]] = self.unpack(field[1], data[:size], dataClassOrCode = dataClassOrCode, field = field[0])
File "/root/PycharmProjects/HoneySMB/libs/structure.py", line 288, in unpack
raise Exception("Unpacked data doesn't match constant value %r should be %r" % (data, answer))
Exception: ("Unpacked data doesn't match constant value b'\\xffSMB' should be 'þSMB'", 'When unpacking field \'ProtocolID | "þSMB | b\'\\xffSMBr\\x00\\x00\\x00\\x00\\x18C\\xc8\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\xfe\\xff\\x00\\x00\\x00\\x00\\x00\\xb1\\x00\\x02PC NETWORK PROGRAM 1.0\\x00\\x02MICROSOFT NETWORKS 1.03\\x00\\x02MICROSOFT NETWORKS 3.0\\x00\\x02LANMAN1.0\\x00\\x02LM1.2X002\\x00\\x02DOS LANMAN2.1\\x00\\x02LANMAN2.1\\x00\\x02Samba\\x00\\x02NT LANMAN 1.0\\x00\\x02NT LM 0.12\\x00\\x02SMB 2.002\\x00\\x02SMB 2.???\\x00\'[:4]\'')
Now it's obvious why this throws an exception. After all, 0xFF does NOT equal ÿ or þ. The question is why is 0xFF the value it tries to write in there in the first place when it should be two different values?
The original python 2 code seems to be quite close to C (using unpack and importing cstring). Is there an obvious benefit to this here or could this be done more simply?
My actual question is:
In the original code, there is no reference to any encoding anywhere. So how is this divined then? Where does it translate 0xFF to ÿ?

Why do I get a MemoryError in 64bit python when doing a replace within a 8MB file? (Bytes)

I have a mitmproxy flow that contains multiple image files. The flow itself is in bytes. I am trying to dump the old images to files, then replace them within the flow with my own images.
However, I hit a Memory Error in Python and I don't understand why. The flow file itself is 8mb, the pictures I am trying to replace the old ones with are small, less then 100kb. There should be plenty of memory for that?
startList = list(re.finditer(b'\xff\xd8',flowContent))
x = 1
for a in startList:
end = flowContent.find(b'\xff\xd9',a.start())
fileContent = flowContent[a.start():end]
fileName = 'image'+str(x)+".jpg"
dumpfile = open('dump/'+fileName,'wb')
dumpfile.write(fileContent)
dumpfile.close()
replace = open('replace/replace'+str(x)+'.jpg','rb')
myImage = Image(replace)
replace.close()
nowTime = datetime.now()
myImage.datetime = nowTime.strftime(DATETIME_STR_FORMAT)
myImage.datetime_digitized = nowTime.strftime(DATETIME_STR_FORMAT)
myImage.datetime_original = nowTime.strftime(DATETIME_STR_FORMAT)
newImage = open('replace/replace'+str(x)+'U.jpg',"wb")
newImage.write(myImage.get_file())
newImage.close()
replaceF = open('replace/replace'+str(x)+'U.jpg','rb')
replaceContent = replaceF.read()
replaceF.close()
flowContent = flowContent.replace(fileContent,replaceContent)
#flowContent = re.sub(fileContent,myImage.get_file(),flowContent)
x = x+1
The error is on this line:
Traceback (most recent call last):
File "E:\SpecialK\flow.py", line 41, in <module>
flowContent = flowContent.replace(fileContent,replaceContent)
MemoryError

pandas error on linux, but working on windows

So, i ran my "ml" model on my local windows machine, everything runs smooth, it just takes 48 hour to fully run every process, naturally i ask the company more procesing power to cut times, they give me a linux simulation server to run my models, but for some reason pandas is giving me the next error:
Traceback (most recent call last):
File "/ANACONDATA/Prediccion_de_Fallas/03_Modelos_y_Scripts/testv14.py", line 894, in <module>
dlist[xx][namer2] = np.where((dlist[xx].too_soon == 0),dlist[xx][column].shift(24) , 0)
File "/opt/anaconda3/lib/python3.9/site-packages/pandas/core/frame.py", line 3643, in __setitem__
self._setitem_array(key, value)
File "/opt/anaconda3/lib/python3.9/site-packages/pandas/core/frame.py", line 3702, in _setitem_array
self._iset_not_inplace(key, value)
File "/opt/anaconda3/lib/python3.9/site-packages/pandas/core/frame.py", line 3721, in _iset_not_inplace
raise ValueError("Columns must be same length as key")
this is the code where i fails (runs ok on windows), tried using pandas 1.3.5, and 1.4.2 same result
features=['AN_Utility_Supply_Press','AN_LPC_ASV_Position',
'AN_Eng_Brg_3Y_Gap',... 200 something list of features]
dlist = {}
turbo= np.unique(dfx2['SAP'])
for xx in (turbo):
dlist[xx]=dfx2.loc[(dfx2['SAP'] == xx)]
for column in dlist[xx][features]:
namer2=[column+'_'+'Lag']
fails here------>dlist[xx][namer2] = np.where((dlist[xx].too_soon == 0),dlist[xx][column].shift(24) , 0)
# namer3=[column+'_'+'Lchg'+"24"]
# dlist[xx][namer3] = np.where((dlist[xx].too_soon == 0),(dlist[xx][column]-dlist[xx][column].shift(24)) , 0)
namer4=[column+'_'+'mean']
dlist[xx][namer4] = np.where((dlist[xx].too_soon == 0),(dlist[xx][column].rolling(min_periods=1, window=feature_window).mean()), dlist[xx][column])
namer5=[column+'_'+'max']
dlist[xx][namer5] = np.where((dlist[xx].too_soon == 0),(dlist[xx][column].rolling(min_periods=1, window=feature_window).max()), dlist[xx][column])
dfx2 = pd.concat(dlist)
dfx2.reset_index(drop=True)
dfx2=dfx2.droplevel(level=0)
am i missing something?, why this happens?

Ok, took some time to figure it out, i tried more versions of pandas until it work, the version is 1.2.4 dont really have an explanation to what happen.

Snap7 get_real command not working, how to fix?

client = snap.client.Client()
client.connect('XXX.XXX.X.XXX', 0, 2) #IP address, rack, slot
db = client.db_get(20)
print(db)
intDB = []
for i in range(1, 122):
reading = client.db_read(20, i, 1)
realReading = snap.util.get_real(reading, 0)
array = [realReading]
intDB.append(array)
print(intDB)
This code is supposed to print a DB in bytearrays and then print an array with the floats values of the PLC output. However, when I run the code, I get the following error message:
Traceback (most recent call last):
File "C:/Users/Asus/PycharmProjects/PLC-Connection/main.py", line 19, in <module>
realReading = snap.util.get_real(reading, 0)
File "C:\Users\Asus\PycharmProjects\PLC-Connection\venv\lib\site-packages\snap7\util.py", line 357, in get_real
real = struct.unpack('>f', struct.pack('4B', *x))[0]
struct.error: pack expected 4 items for packing (got 1)

I think that the problem is reading the data:
reading = client.db_read(20, i, 1)
20 is the datablock, i is the index, and you read only 1 byte (3rd parameter).
For retrieving a real, you need 4 bytes read out.

Python ValueError: chr() arg not in range(256)

So I am learning python and redoing some old projects. This project involves taking in a dictionary and a message to be translated from the command line, and translating the message. (For example: "btw, hello how r u" would be translated to "by the way, hello how are you".
We are using a scanner supplied by the professor to read in tokens and strings. If necessary I can post it here too. Heres my error:
Nathans-Air-4:py1 Nathan$ python translate.py test.xlt test.msg
Traceback (most recent call last):
File "translate.py", line 26, in <module>
main()
File "translate.py", line 13, in main
dictionary,count = makeDictionary(commandDict)
File "/Users/Nathan/cs150/extra/py1/support.py", line 12, in makeDictionary
string = s.readstring()
File "/Users/Nathan/cs150/extra/py1/scanner.py", line 105, in readstring
return self._getString()
File "/Users/Nathan/cs150/extra/py1/scanner.py", line 251, in _getString
if (delimiter == chr(0x2018)):
ValueError: chr() arg not in range(256)
Heres my main translate.py file:
from support import *
from scanner import *
import sys
def main():
arguments = len(sys.argv)
if arguments != 3:
print'Need two arguments!\n'
exit(1)
commandDict = sys.argv[1]
commandMessage = sys.argv[2]
dictionary,count = makeDictionary(commandDict)
message,messageCount = makeMessage(commandMessage)
print(dictionary)
print(message)
i = 0
while count < messageCount:
translation = translate(message[i],dictionary,messageCount)
print(translation)
count = count + 1
i = i +1
main()
And here is my support.py file I am using...
from scanner import *
def makeDictionary(filename):
fp = open(filename,"r")
s = Scanner(filename)
lyst = []
token = s.readtoken()
count = 0
while (token != ""):
lyst.append(token)
string = s.readstring()
count = count+1
lyst.append(string)
token = s.readtoken()
return lyst,count
def translate(word,dictionary,count):
i = 0
while i != count:
if word == dictionary[i]:
return dictionary[i+1]
i = i+1
else:
return word
i = i+1
return 0
def makeMessage(filename):
fp = open(filename,"r")
s = Scanner(filename)
lyst2 = []
string = s.readtoken()
count = 0
while (string != ""):
lyst2.append(string)
string = s.readtoken()
count = count + 1
return lyst2,count
Does anyone know whats going on here? I've looked through several times and i dont know why readString is throwing this error... Its probably something stupid i missed

chr(0x2018) will work if you use Python 3.
You have code that's written for Python 3 but you run it with Python 2. In Python 2 chr will give you a one character string in the ASCII range. This is an 8-bit string, so the maximum parameter value for chris 255. In Python 3 you'll get a unicode character and unicode code points can go up to much higher values.

The issue is that the character you're converting using chr isn't within the range accepted (range(256)). The value 0x2018 in decimal is 8216.
Check out unichr, and also see chr.