bh_sim.py

import socket
import struct

BECKHOFF_TCP_PORT = 48898   # 0xBF02
BECKHOFF_UDP_PORT = 48899   # 0xBF03
BECKHOFF_UDP_PORT2 = 48847  # 0xBECF

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind(('0.0.0.0', BECKHOFF_TCP_PORT))
s.listen(5)

while True:
    print('accepting...')
    (sock, addr) = s.accept()
    print('connected!')
    while 1:
        print('read message...')
        try:
            data = b''
            while len(data) < 6:
                newdata = sock.recv(6 - len(data))
                if not newdata:
                    raise ValueError("connection broken")
                data += newdata
                print(f'data: {data!r}')
            _zero, _size = struct.unpack('<HI', data)
            if _zero != 0:
                raise ValueError('Wrong Format (zero != 0)')
            while len(data) < _size + 6:
                data += sock.recv(_size + 6 - len(data))
                if len(data) > _size + 6:
                    print(f'Too much data received: {len(data)} {_size + 6} '
                          f'{data!r}')
        except Exception as e:
            print('Exception reading from master:', e)
            break
        print('return message')
        data = data[:6] + data[14:22] + data[6:14] + data[22:]
        sock.sendall(data)