Microduino ENC Network (6)

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This tutorial will show you how to write a sketch to update a DNS record hosted by one of the most famous Dynamic DNS service providers, no-ip.


  • Other equipment
    • USB cable

Dynamic IP addresses

If you connect to Internet using a home or mobile connection, you’ll probably have a dynamic public IP address, that is it changes every time you connect.

If you need to talk to a device on Internet, you need to write – in the message you send on the net – its public IP address: if this IP is dynamic, you may not know it.

Dynamic DNS

In Internet you can find free Dynamic DNS (DDNS) services: they allow you to associate a name you choose with an IP address and they allow you to keep that association updated.

The update could be done in different ways:

  • using a client running on your PC;
  • with a feature present in your router:
  • asking Arduino to do it for us.


One of the most used site offering dynamic DNS service is No-IP.

If you register for free to No-IP Free service, you can configure up to 5 hosts for Hosts/Redirects feature:


For this tutorial, I registered the following host: enctutorial.no-ip.info.

DDNS Client

Every DDNS client performs the following steps:

  • gets the actual public IP (asking the router, an external website…);
  • compares that IP with the one resolved from DNS alias;
  • if they are different, it updates the DNS record via service provider's API.


  • Microduino-ENC28J60
  • Microduino-RJ45
  • Microduino-Core
  • Microduino-FT232R

Stack all modules and then connect the ethernet cable, as follows:



Refer to ENCnetworksix


Step 1: Download the EtherCard library and copy to your libraries fold of IDE, then restart IDE. https://github.com/jcw/ethercard

Step 2: Explain the program:

Public IP: To find the actual public IP, I wrote a simple PHP page on my website:


Microduino sketch gets that page and parse the IP address.

DNS record and comparison:

//Sketch calls dnsLookup() method to resolve actual IP for DNS record; it then converts the result in a String object to use its compareTo() method to compare the two IP addresses:

     if(!ether.dnsLookup(noIP_host)) { 
     } else {
     for(int i = 0; i < 4; i++) {
       dnsIp = dnsIp + String(ether.hisip[i]);
       if(i < 3) dnsIp = dnsIp + ".";
     if(actualIp.compareTo(dnsIp) == 0) {
       Serial.println("No update needed :)");
     } else {
       Serial.println("Update needed :(");
       actual_status = STATUS_NOIP_NEEDS_UPDATE;

Authentication: You have to authenticate to No-IP before being allowed to update any records.


You have to assign to that constant the base64 encoded value of the string username:password.


Step 3: Compile the code and download it.

Step 4: Check if can access the Microduino.


Arduino correctly found a difference between public IP and DNS record so it updated No-IP record. After a while, it performed another check and this time the two IP addresses were equals so no update was required.