DDNS update client script

# python script to check for IP changes
# and update a Free DNS account via the Direct URL method
import syslog
from urllib import urlopen
from socket import getaddrinfo

# insert your Direct URL and DDNS host below
checkurl = 'http://freedns.afraid.org/dynamic/check.php'
directurl = 'https://thedirectupdateURLinyourFreeDNSaccount.com'
ddnshost = 'hostname.you.selected.com'

def ddns_ip():
# effectively perform a dns lookup
    try:
        ddnsip = getaddrinfo(ddnshost,'80')[0][4][0]
        syslogwrite('Host ' + ddnshost + ' resolves to: ' + ddnsip)
    except:
        ddnsip = '0.0.0.0'
        syslogwrite('DNS lookup failure')
    return(ddnsip)
# end ddns_ip

def actual_ip():
# get ip detected by freedns website
    try:
        actualip = urlopen(checkurl).read().split()[3]
        syslogwrite('External IP detected as: ' + actualip)
    except:
        actualip = '0.0.0.0'
        syslogwrite('External IP detection failure')
    return(actualip)
# end actual_ip

def update_ip():
# perform Direct URL update
    try:
# we're not interested in the server's response
        dummy = urlopen(directurl).read()
        syslogwrite('Updating Free DNS IP via Direct URL.')
    except:
        syslogwrite('Direct URL update failed.')
    return 0
# end update_ip

def syslogwrite(message):
    syslog.syslog(syslog.LOG_INFO,message)
    return 0
# end syslogwrite

# main
syslogwrite('Automatic update process started.')
ddnsip = ddns_ip()
actualip = actual_ip()
# if lookup was successful
if not ((ddnsip == '0.0.0.0') or (actualip == '0.0.0.0')):
# if IPs don't match, carry out update
    if not ddnsip == actualip:
        update_ip()
# else if lookup was not successful
else:
    syslogwrite('An error occured.')
syslogwrite('Automatic update process completed.')
# end