DDNS Synch

Internet connected devices and web pages residing in a home computer needs a static (stable) IP address to allow access from a remote location.

ISPs will provide a static IP address at an additional cost.

An alternative is to use a Dynamic Domain Name Server (DDNS) service to associate a chosen domain name to an IP address.

A dynamic IP address provided by a router’s DHCP function can be used with a DDNS if you can maintain / update the DDNS entry with the current IP address.

Here’s how to do this with an Arduino and a web pgrogram (HTML/PHP).

  • Write an Arduino sketch to query a web page periodically. Do not flood the website with queries. Once every 15 minutes is sufficient.
  • Write a web page (PHP/HTML program)
    • Receive the query
    •  Capture the remote IP address
    • Compare it to the last captured IP address saved in a file.
      • if equal:
        • write the IP address to the last IP address file
        • exit.
      • If not equal:,
        • write the IP address and current to the last IP address file.
        •  update the DDNS service with the new IP address and associated domain name.
        • exit.
    • (Optional) Write a web page to query the last IP address file and display the  latest IP address and date/time changed.

Note:  to prevent unintentional updates to the DDNS; add a parameter to the URL and check it for validity. Ignore and exit if not valid.

ex: http://myhost.net/ddns-synch.php? youare=forsure

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