import socket, zlib

HOST = "127.0.0.1"  # Standard loopback interface address (localhost)
PORT = 2000  # Port to listen on (non-privileged ports are > 1023)

def calculate_crc(data):
    # Calculate the CRC32 checksum of the data
    crc = zlib.crc32(data)
    # Convert the CRC32 value to a 4-byte big-endian byte array
    crc_bytes = crc.to_bytes(4, byteorder='big')
    return crc_bytes

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.bind((HOST, PORT))
    s.listen()
    while True:
        try:
            conn, addr = s.accept()
            with conn:
                print(f"Connected by {addr}")
                while True:
                    data = conn.recv(1024)
                    if not data:
                        break
                    print(f'RECV: {data.hex()} [{len(data)}]')
                    if data[0x11] == 0x01:
                        pckt = bytearray([0x01])
                        pckt.extend([0x00, 0x00, 0x00, 0x00]) # src
                        pckt.extend([0x00, 0x00, 0x00, 0xFF]) # dest
                        pckt.extend([0x00, 0x00, 0x00, 0x00]) # packet_id
                        pckt.extend(data[0x09:0x0D]) # reply_to
                        pckt.extend([0x01]) # command
                        pckt.extend([0x00, 0x04]) # data_length
                        pckt.extend([0x00, 0x00, 0x00, 0xFF])

                        # Calculate CRC for the received data
                        crc = calculate_crc(pckt)
                        # Append the CRC value to the data
                        data_with_crc = pckt + crc
                        # Send the modified data (with CRC) back to the client
                        conn.sendall(data_with_crc)
                        print(f'SEND: {data_with_crc.hex()} [{len(data_with_crc)}]')
        except:
            s.close()