How to do it...

Let us define a find_service_name() function, where the getservbyport() socket class function will be called with a few ports, for example, 80, 25. We can use Python's for-in loop construct.

Listing 1.4 shows finding_service_name 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 
 
def find_service_name(): 
    protocolname = 'tcp' 
    for port in [80, 25]: 
        print ("Port: %s => service name: %s" %(port, socket.getservbyport(port, protocolname))) 
     
    print ("Port: %s => service name: %s" %(53, socket.getservbyport(53, 'udp'))) 
     
if __name__ == '__main__': 
    find_service_name() 
 

If you run this script, you will see the following output:

$ python 1_4_finding_service_name.py 
    
Port: 80 => service name: http
Port: 25 => service name: smtp
Port: 53 => service name: domain
    

This indicates that http, smtp, and domain services are running on the ports 80, 25, and 53 respectively.