DHCP — wifi join করলেই address কোথা থেকে আসে

import json, socket, threading, time

GROUP, PORT = '239.255.0.67', 6767      # simulation segment

def tx(msg):
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    s.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 1)
    s.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_IF,
                 socket.inet_aton('127.0.0.1'))
    s.sendto(json.dumps(msg).encode(), (GROUP, PORT)); s.close()

class Peer(threading.Thread):
    def __init__(self, name):
        super().__init__(daemon=True)
        self.name = name
        self.s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        self.s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
        self.s.bind(('', PORT))
        self.s.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP,
                          socket.inet_aton(GROUP) + socket.inet_aton('127.0.0.1'))
    def log(self, text):
        print(f'[{time.strftime("%H:%M:%S")}] {self.name:<7} {text}')

class Server(Peer):
    def __init__(self, name):
        super().__init__(name)
        self.pool_next, self.leases = 101, {}   # 192.168.1.101 … .199
        self.opts = {'mask': '255.255.255.0', 'router': '192.168.1.1',
                     'dns': ['1.1.1.1'], 'lease': 3600}
        threading.Thread(target=self.loop, daemon=True).start()
    def loop(self):
        while True:
            msg = json.loads(self.s.recvfrom(4096)[0])
            if msg['type'] == 'DISCOVER':
                ip = self.allocate(msg['chaddr'])
                self.log(f"OFFER  {ip} → {msg['chaddr']}")
                tx({'type': 'OFFER', 'siaddr': self.name, 'yiaddr': ip,
                    'xid': msg['xid'], 'opts': self.opts})
            elif msg['type'] == 'REQUEST':
                if msg['siaddr'] != self.name:
                    continue                    # client অন্য server নিয়েছে
                self.leases[msg['chaddr']] = msg['yiaddr']
                self.log(f"ACK    {msg['yiaddr']} → {msg['chaddr']}")
                tx({'type': 'ACK', 'yiaddr': msg['yiaddr'], 'xid': msg['xid'],
                    'opts': self.opts})
    def allocate(self, mac):
        if mac in self.leases: return self.leases[mac]
        used = set(self.leases.values())
        while f'192.168.1.{self.pool_next}' in used: self.pool_next += 1
        return f'192.168.1.{self.pool_next}'

class Client(Peer):
    def __init__(self, mac):
        super().__init__('client'); self.mac = mac
    def recv_matching(self, typ, xid):
        while True:
            m = json.loads(self.s.recvfrom(4096)[0])
            if m['type'] == typ and m['xid'] == xid: return m
    def dora(self):
        xid = '3a1fb207'
        self.log("DISCOVER  0.0.0.0:68 → 255.255.255.255:67")
        tx({'type': 'DISCOVER', 'chaddr': self.mac, 'xid': xid})
        o = self.recv_matching('OFFER', xid)
        self.log(f"OFFER {o['yiaddr']} ({o['siaddr']}) — REQUEST broadcast")
        tx({'type': 'REQUEST', 'chaddr': self.mac, 'xid': xid,
            'siaddr': o['siaddr'], 'yiaddr': o['yiaddr']})
        a = self.recv_matching('ACK', xid)
        self.log(f"BOUND  {a['yiaddr']}/24  router={a['opts']['router']} "
                 f"dns={a['opts']['dns']} lease={a['opts']['lease']}s")

if __name__ == '__main__':
    Server('alpha'); Server('beta')
    time.sleep(0.3)
    Client('aa:bb:cc:dd:ee:01').dora()
    time.sleep(0.3)

Output (server-race ভেদে alpha/beta বদলাতে পারে — বাস্তবের মতো):

[client]     DISCOVER  0.0.0.0:68 → 255.255.255.255:67
[alpha]      OFFER  192.168.1.101 → aa:bb:cc:dd:ee:01
[beta]       OFFER  192.168.1.101 → aa:bb:cc:dd:ee:01
[client]     OFFER 192.168.1.101 (alpha) — REQUEST broadcast
[alpha]      ACK    192.168.1.101 → aa:bb:cc:dd:ee:01
[client]     BOUND  192.168.1.101/24  router=192.168.1.1 ...

নিজে বাড়ান: (১) rogue-server (ভিন্ন gateway offer) যোগ করে দেখুন siaddr-match logic-ই একমাত্র রক্ষা; (২) T1 renewal — half-lease-এ ‘unicast’ simulation; (৩) pool-exhaustion handling — ৯৯ client নামান।