Download and provide interface to port to service (better then socket.getservbyport, as /etc/services is not always complete)

port_to_service.py

#!/usr/bin/env python

import os
import csv
import requests

CSV_DIR = 'resources'
CSV_PATH = 'resources/service-names-port-numbers.csv'
URL = 'https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv'

def _download_and_save(outfile):
    data = requests.get(URL).content
    open(outfile, 'w').write(data)

class PortToName(object):
    def __init__(self, csv_path=CSV_PATH):
        self.map = {}
        self.csv_path = csv_path
        if not os.path.exists(CSV_DIR):
            os.mkdir(CSV_DIR)
        if not os.path.exists(CSV_PATH):
            _download_and_save(CSV_PATH)

        self._load_csv()

    def _load_csv(self):
        with open(self.csv_path) as fh:
            for row in csv.DictReader(fh, delimiter=','):
                port = row['Port Number']
                service = row['Service Name']

                if service == '':
                    continue

                self.map[port] = service

    def resolve(self, port, filler='-'):
         return self.map.get(str(port), filler)

if __name__ == '__main__':
    port_resolver = PortToName()
    print port_resolver.resolve(445)
    print port_resolver.resolve('445')