A simple authoritative DNS server which returns the same answer for all questions

auth_dns_serve.py

import time
import socket
import select
import sqlite3
import dns.message
import dns.exception

DNS_SERVER_PORT = 53
IP4_ADDR = '0.0.0.0' # IPv4 address to return
IP6_ADDR = '::' # IPv6 address to return (if you want to support IPv6)

def handle_dns_query(raw_query):
    """
        Return the name and wire-formated DNS response
    """
    query = dns.message.from_wire(raw_query)
    question = str(query.question[0])
    name, rtype = [r.strip() for r in question.split('IN')]

    if rtype == 'A':
        ip_resp = IP4_ADDR
    elif rtype == 'AAAA':
        ip_resp = IP6_ADDR
    else:
        print('Only A and AAAA are supoprted')
        raise NotImplementedError

    response = dns.message.make_response(query)
    rrset = dns.rrset.from_text(name, 10, 1, rtype, ip_resp)
    response.answer.append(rrset)
    wire_resp = response.to_wire()

    return name, wire_resp


def store(db, name, conn):
    identifier = int(name.split('.')[0])
    ip_addr, *_ = conn
    db.execute('''
        insert into ip (id, ip_addr) values (?, ?)
    ''', (identifier, ip_addr))
    db.commit()


def main_loop():
    db = sqlite3.connect('store.db')
    db.execute('PRAGMA journal_mode=WAL;')
    db.execute('''
        create table if not exists ip (
            id integer primary key not null,
            ip_addr text not null
        );
    ''')
    port = DNS_SERVER_PORT
    sock6 = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM) # if you want to be IPv6-ready
    sock6.bind(('::', port))
    sock4 = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    sock4.bind(('0.0.0.0', port)) # listen on public interfaces
    socks = [ sock6, sock4 ]

    while True:
        rlist, _, _ = select.select(socks, [], [])
        for conn in rlist:
            dgram, addr = conn.recvfrom(4096)

            # Resolve
            try:
                name, wire_resp = handle_dns_query(dgram)
            except NotImplementedError:
                continue # ignore the client

            # Store
            try:
                store(db, name, addr)
            except (sqlite3.Error, ValueError) as e:
                print(e)
                continue

            # Respond
            conn.sendto(wire_resp, addr)


if __name__ == '__main__':
    while True:
        try:
            main_loop()
        except Exception as e:
            print(e)
        time.sleep(3)

I'm getting below error Please help on this..

[Errno 48] Address already in use