Python script that 'emulates' topsee devices

topsee_dev.py

#!/usr/bin/env python3

from socket import socket
import xml.etree.ElementTree as ET

magic = b'\x58\x91\x58\x51'

auth_response = """<?xml version="1.0" encoding="GB2312" ?>
<XML_TOPSEE>
<MESSAGE_HEADER
Msg_type="USER_AUTH_MESSAGE"
Msg_code="CMD_USER_AUTH"
Msg_flag="0" />
<MESSAGE_BODY>
<USER_AUTH_RESPONSE
Sessionid="20150226100807_2ba514d2ca8ef870"
Group="Administrator"
/>
</MESSAGE_BODY>
</XML_TOPSEE>
""".encode()

heartbeat_response = """<?xml version="1.0" encoding="GB2312" ?>
<XML_TOPSEE>
<MESSAGE_HEADER
Msg_type="AUXPTZ_HEARTBEAT_MESSAGE"
Msg_code="CMD_HEARTBEAT"
Msg_flag="0"
/>
<MESSAGE_BODY>
</MESSAGE_BODY>
</XML_TOPSEE>
""".encode()

def to_hex(a):
    return ''.join("%02x" % x for x in a)

server = socket()
server.bind(("0.0.0.0", 8091))
server.listen(1)

client, address = server.accept()

print("Connection from",address)

while True:
    client.recv(4) # magic
    length = client.recv(4)
    length = int.from_bytes(length, "little")
    xml = ET.fromstring(client.recv(length).decode())
    hdr = xml.find('./MESSAGE_HEADER')
    msg_code = hdr.attrib['Msg_code']

    print(msg_code, length)

    if  (msg_code == "CMD_USER_AUTH"):
        client.send(magic)
        client.send(len(auth_response).to_bytes(4, "little"))
        client.send(auth_response)

    elif(msg_code == "CMD_HEARTBEAT"):
        client.send(magic)
        client.send(len(heartbeat_response).to_bytes(4, "little"))
        client.send(heartbeat_response)

    else:
        print(ET.tostring(xml))