Sample DNS server

dns_server.py

from typing import Tuple

from curio import socket
import curio
import dnslib as dns


class Server:
    def __init__(self) -> None:
        self.port = 53
        self._sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

    async def start(self) -> None:
        self._sock.bind(('0.0.0.0', self.port))

        while True:
            packet, addr = await self._sock.recvfrom(512)
            await self.on_packet(packet, addr)
        await self._sock.close()

    async def on_packet(self, packet: bytes, addr: Tuple[str, int]) -> None:
        dns_query = dns.DNSRecord.parse(packet)
        print(dns_query, '\n')
        await self._sock.sendto(make_reply(dns_query), addr)


def make_reply(record: dns.DNSRecord) -> bytes:
    """Makes a stub response."""
    resp = record.reply()
    query_name = record.questions[0].qname
    resp.add_answer(
        dns.RR(query_name, dns.QTYPE.A, rdata=dns.A('1.2.3.4'), ttl=60))
    return resp.pack()


def main() -> None:
    server = Server()
    curio.run(server.start)


if __name__ == '__main__':
    main()

requirements.txt

curio==0.8
dnslib==0.9.7