Utility to check changes of Dynamic IP addresses. It emails the user every 6 hours if the IP changes in that period. This is better then having a domain because you computer is a bit more secure since only you know the IP to access it.

check_ip.py

import subprocess
import time
import smtplib
import string

# Author Nuno Khan
# Utility to check dynamic ip addresses

def save_new_Ip(p):
    ip=""
    f = open('ip.log', 'a')
    for line in p.stdout.readlines():
        ip= ip+line
        f.write(ip)
        print ("You IP address is {ip}").format(**locals())
    f.close()
    return ip.strip()

def compare_ip():
    fileHandle = open ( 'ip.log',"r" )
    lineList = fileHandle.readlines()
    fileHandle.close()	
    if lineList[-2] != lineList[-1] :
        return True
    else:
        return False

def sendMail(TO,text):
    username="xxx"
    password="xxx"
    HOST = "smtp.gmail.com:587"
    SUBJECT = "Your IP address changed"
    FROM = "Khan Desktop"
    BODY = string.join(("From: %s" % FROM,"To: %s" % TO,"Subject: %s" % SUBJECT ,"",text), "\r\n")

    server = smtplib.SMTP(HOST)
    try:
        server.set_debuglevel(False)
        # identify ourselves, prompting server for supported features
        server.ehlo()
        # If we can encrypt this session, do it
        if server.has_extn('STARTTLS'):
            server.starttls()
            server.ehlo() # re-identify ourselves over TLS connection
            server.login(username,password)
            server.sendmail(FROM, [TO], BODY)
    finally:
            server.quit()

def check_ip():
    print ("Checking IP address")
    command="wget -q -O - checkip.dyndns.org|sed -e 's/.*Current IP Address: //' -e 's/<.*$//'"
    p = subprocess.Popen(command, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    new_ip=save_new_Ip(p)
    if(compare_ip()):
        sendMail("[email protected]",new_ip)
    retval = p.wait()
    print ("In 6 hours the IP address will be checked again")

def main():
    while (True):
        re_check = 21600 # 6 hours
        check_ip()
        time.sleep(re_check)

if __name__ == "__main__":
    main()