We import dns.reversename of dnspython to do a simple exercise of finding the reverse name of an address from the given address. We use dns.resolver to find the address that an IP address resolves to be.

Listing 11.2 gives the domain information for a given IP address as follows:

#!/usr/bin/env python 
# Python Network Programming Cookbook, Second Edition 
  -- Chapter - 11 
# This program is optimized for Python 2.7.12 and
  Python 3.5.2. 
# It may run on any other version with/without
  modifications. 
 
 
import argparse 
import dns.reversename 
import dns.resolver 
 
def main(address): 
    n = dns.reversename.from_address(address) 
    print(n) 
    print(dns.reversename.to_address(n)) 
 
    try: 
        # Pointer records (PTR) maps a network 
          interface (IP) to the host name. 
        domain = str(dns.resolver.query(n,"PTR")[0]) 
        print(domain) 
    except Exception as e: 
        print ("Error while resolving %s: %s" %(address, e)) 
 
 
if __name__ == '__main__': 
    parser = argparse.ArgumentParser(description='DNS Python') 
    parser.add_argument('--address', action="store",
    dest="address",  default='127.0.0.1') 
    given_args = parser.parse_args()  
    address = given_args.address 
    main (address) 

We run this recipe with various inputs for addresses. First with localhost, followed by two valid addresses in the internet, and then an invalid address.

$ python 11_2_dns_host_with_dnspython.py --address="127.0.0.1"
1.0.0.127.in-addr.arpa.
b'127.0.0.1'
localhost.
    
$ python 11_2_dns_host_with_dnspython.py --address="216.58.199.78"
78.199.58.216.in-addr.arpa.
b'216.58.199.78'
syd15s01-in-f78.1e100.net.
    
$ python 11_2_dns_host_with_dnspython.py --address="172.217.19.193"
193.19.217.172.in-addr.arpa.
b'172.217.19.193'
ams16s31-in-f1.1e100.net.
    
$ python 11_2_dns_host_with_dnspython.py --address="52.95.3.61"
61.3.95.52.in-addr.arpa.
b'52.95.3.61'
Error while resolving 52.95.3.61: The DNS query name does not exist: 61.3.95.52.in-addr.arpa.