How to decode a string of bytes in python?

Question

Python

Initially, the socket sends to python

14:46:37:820 отправлено: 33 байт
 7e 41 01 00 00 00 00 00 10 1d 43 a1 5f 01 1d 43
 a1 5f 30 c4 55 01 f0 a8 fb 01 00 00 00 00 00 00 e4

~A  Size = 1
numPage = 0  Code = 4096  Time = 1604403997  StateGauge = 1  LastTime = 1604403997  Lat = 22398000  Lon = 33270000  Speed = 0  Course = 0

The python itself comes

b'~A\x01\x00\x00\x00\x00\x00\x10\x1dC\xa1_\x01\x1dC\xa1_0\xc4U\x01\xf0\xa8\xfb\x01\x00\x00\x00\x00\x00\x00\xe4'

Python code:

spoiler

import socket
import re

# Задаем адрес сервера
SERVER_ADDRESS = ('localhost', 8686)

# Настраиваем сокет
server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_socket.bind(SERVER_ADDRESS)
server_socket.listen(10)
print('server is running, please, press ctrl+c to stop')

# Слушаем запросы
# Особенности протокола
while True:
    connection, address = server_socket.accept()
    print("new connection from {address}".format(address=address))
# Соединение всегда инициализирует навигатор, через handshake  мы должны ему сразу ответить!
#	0x40, 0x4e, 0x54, 0x43, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x03, 0x00, 0x45, 0x5e,0x2a, 0x3c, 0x53,
#    connection.send(bytes('@NTC\x40\x4e\x54\x43\x00\x00\x00\x01\x00\x00\x00\x03\x00\x45\x5e*<S', encoding='UTF-8'))

#Согласование протокола  FLEX v1
#protocol answer
#0x40, 0x4e, 0x54, 0x43,0x00,0x00,0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x09, 0x00, 0xb1, 0xa0, 0x2a, 0x3c, 0x46, 0x4c, 0x45, 0x58, 0xb0, 0x0a, 0x0a,
#    connection.send(bytes('x40\x4e\x54\x43\x00\x00\x00\x00\x00\x01\x00\x00\x00\x09\x00\xb1\xa0\x2a\x3c\x46\x4c\x45\x58\xb0\x0a\x0a', encoding='UTF-8'))
    
    while 1:
        data = connection.recv(8192)
        print(data)
        results = [
            dict(re.findall(r"(\d{4})([\d.]+)", string))
            for string in filter(
            bool,  # non-empty
            data.decode('ascii', 'ignore').split("&&"),
        )
        ]
        print(data.decode('ascii', 'ignore'))
        print(data.decode('cp866'))

What is my error, or is it some wrong bytes?)

Answer 1

Use struct.unpack() it's the best friend of all reverse engineers.

a = b'\x7e\x41\x01\x00\x00\x00\x00\x00\x10\x1d\x43\xa1\x5f\x01\x1d\x43\xa1\x5f\x30\xc4\x55\x01\xf0\xa8\xfb\x01\x00\x00\x00\x00\x00\x00\xe4'
Size,numPage,Code,Time,StateGauge,LastTime,Lat,Lon,Speed,Course, = struct.unpack("<2xBIHIBIIIHH",a[:30])