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#!/usr/bin/env python3
# This is just a toy, real code would check that the received message
# really was a NOTIFY, and otherwise handle errors.
import socket
from typing import cast
import dns.flags
import dns.message
import dns.name
import dns.rdataclass
import dns.rdatatype
address = "127.0.0.1"
port = 53535
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.bind((address, port))
while True:
(wire, address) = s.recvfrom(512)
notify = dns.message.from_wire(wire)
try:
soa = notify.find_rrset(
notify.answer, notify.question[0].name, dns.rdataclass.IN, dns.rdatatype.SOA
)
# Do something with the SOA RR here
print("The serial number for", soa.name, "is", soa[0].serial)
except KeyError:
# No SOA RR in the answer section.
pass
response = dns.message.make_response(notify) # type: dns.message.Message
response.flags |= dns.flags.AA
wire = response.to_wire(cast(dns.name.Name, response))
s.sendto(wire, address)
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