When you would like to deal with low-level network functions, sometimes, the usual string notation of IP addresses are not very useful. They need to be converted to the packed 32-bit binary formats.

The Python socket library has utilities to deal with the various IP address formats. Here, we will use two of them: inet_aton() and inet_ntoa().

Let us create the convert_ip4_address() function, where inet_aton() and inet_ntoa() will be used for the IP address conversion. We will use two sample IP addresses, 127.0.0.1 and 192.168.0.1.

Listing 1.3 shows ip4_address_conversion as follows:

#!/usr/bin/env python
# Python Network Programming Cookbook,
  Second Edition -- Chapter - 1
# 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 socket
    from binascii import hexlify
    
    
    def convert_ip4_address():
        for ip_addr in ['127.0.0.1', '192.168.0.1']:
            packed_ip_addr = socket.
                             inet_aton(ip_addr)
            unpacked_ip_addr = socket.inet_ntoa
                               (packed_ip_addr)
            print ("IP Address: %s => Packed: %s, 
                    Unpacked: %s" %(ip_addr, 
                    hexlify(packed_ip_addr), 
                    unpacked_ip_addr))
    
    if __name__ == '__main__':
        convert_ip4_address()
  

Now, if you run this recipe, you will see the following output:

$ python 1_3_ip4_address_conversion.py 
IP Address: 127.0.0.1 => Packed: 7f000001, Unpacked: 
127.0.0.1
IP Address: 192.168.0.1 => Packed: c0a80001, Unpacked: 192.168.0.1
  

In this recipe, the two IP addresses have been converted from a string to a 32-bit packed format using a for-in statement. Additionally, the Python hexlify function is called from the binascii module. This helps to represent the binary data in a hexadecimal format.