Simple DynDNS update script

update.py

import argparse, socket, requests, json, os

parser = argparse.ArgumentParser()

parser.add_argument('--username', type=str, help="DynDns Username", required=True)
parser.add_argument('--password', type=str, help="DynDns Password", required=True)
parser.add_argument('--url', type=str, help="Update url with <ipaddr> and <ip6addr> parameters", required=True)
args = parser.parse_args()

# attempt to get the server's ipv4 and ipv6 addresses
addrs = socket.getaddrinfo('api.jangxx.com', 443)

ipv4_addrs = [addr[4][0] for addr in addrs if addr[0] == socket.AF_INET]
ipv6_addrs = [addr[4][0] for addr in addrs if addr[0] == socket.AF_INET6]

ipaddr = None
if len(ipv4_addrs) > 0:
	ipv4_url = "http://" + str(ipv4_addrs[0]) + "/i/ip"
	ipv4_req = requests.get(ipv4_url, headers={ "Host": "api.jangxx.com" })
	ipaddr = ipv4_req.text

ip6addr = None
if len(ipv6_addrs) > 0:
	ipv6_url = "http://[" + str(ipv6_addrs[0]) + "]/i/ip"
	ipv6_req = requests.get(ipv6_url, headers={ "Host": "api.jangxx.com" })
	ip6addr = ipv6_req.text

ipfile_exists = os.path.isfile("ips.json")

if ipfile_exists:
	ipfile = open("ips.json", "r+")
	try:
		old_ips = json.load(ipfile)
	except:
		old_ips = { "ipaddr": None, "ip6addr": None }
		ipfile.close()
		ipfile = open("ips.json", "w+")
		json.dump(old_ips, ipfile)

	ipfile.close()
	
else:
	ipfile = open("ips.json", "w+")
	old_ips = { "ipaddr": None, "ip6addr": None }
	json.dump(old_ips, ipfile)
	ipfile.close()

# check if we need to update the ips
if (old_ips["ipaddr"] != ipaddr and ipaddr is not None) or (old_ips["ip6addr"] != ip6addr and ip6addr is not None):
	print("Updating addresses on the server")
	
	# assemble update url
	update_url = args.url
	if ipaddr:
		update_url = update_url.replace("<ipaddr>", ipaddr)
	if ip6addr:
		update_url = update_url.replace("<ip6addr>", ip6addr)

	resp = requests.get(update_url, auth=requests.auth.HTTPBasicAuth(args.username, args.password))
	print("Server reply:", resp.text)

	# store updated addresses in the ips file

	old_ips["ipaddr"] = ipaddr
	old_ips["ip6addr"] = ip6addr

	ipfile = open("ips.json", "w+")
	json.dump(old_ips, ipfile)
	ipfile.close()
else:
	print("Nothing to update.")