UDP broadcast with hmac and sequence ID

udprecv.py

#!/usr/bin/env python3

import socket, hashlib, struct

client = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP) # UDP
client.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
client.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)

client.bind(("", 37700))

def receive(hmac):
    data, addr = client.recvfrom(1024)

    if len(data) < 45: return
    magic = data[:2]
    hash = data[3:35]
    full_body = data[36:]
    seq_id = struct.unpack(">Q", full_body[:8])
    body = full_body[9:]

    comp_hash = hashlib.sha256(hmac.encode("utf8") + full_body).digest()
    if comp_hash == hash:
        return (seq_id, body.decode("utf8"))

while True:
    print(receive("Jeger"))

udpt.py

#!/usr/bin/env python3

from socket import *
import time, hashlib, struct, datetime


cs = socket(AF_INET, SOCK_DGRAM)
cs.setsockopt(SOL_SOCKET, SO_REUSEPORT, 1)
cs.setsockopt(SOL_SOCKET, SO_BROADCAST, 1)

def send_message(message, hmac):
        # sequence + LF + message
        message_body   = struct.pack(">Q", int(datetime.datetime.now().timestamp())) + b"\n" + message.encode("utf8")
        # digest of hmac + full message hash
        message_digest = hashlib.sha256(hmac.encode("utf8") + message_body).digest()
        # "DN" + LF + digest + LF + body (sequence + LF + message)
        composed_message = b"DN\n" + message_digest + b"\n" + message_body
        # broadcast defaults to 255.255.255.255 which is technically not correct for this net but it works idk 
        cs.sendto(composed_message, ('<broadcast>', 37700))

send_message('{"value": 105}', "Jeger")