Arduino: How to get IP Address for a URL

 I was revisiting an Arduino program that was setting the real-time clock on an Arduino MKR 1010 using the services of an NTP timeserver. The problem was that the IP address I had been using to lookup the time was not (currently) valid. I soon found an alternative but wondered if I could use a time server URL to lookup a currently valid IP address to pass to a WiFiUDP object instance.

I took a look in the WiFi.cpp file that defines the WiFi class and found a handy function that looked like just the thing.

int WiFiClass::hostByName(const char* aHostname, IPAddress& aResult)
	return WiFiDrv::getHostByName(aHostname, aResult);

The following short Arduino program shows how to retrieve the IP address of a URL and store it in an arduino::IPAddress object. [Arduino documentation for IPAddress object.]

#include <WiFiNINA.h>
const char* mySSID = SECRET_SSID; // your WiFi SSID
const char* myPass = SECRET_PASSWORD; // Your WiFi password

template inline Print &operator<<(Print &obj, T arg) {
  obj.print(arg); return obj;}

void setup() {
  while (!Serial) {}
void testHost() {
  IPAddress lookup;
  int res = WiFi.hostByName("", lookup);
  Serial << "Test Lookup\n";
  Serial << lookup << '\n';
void connectToWiFi() {
  if (WiFi.status() != WL_CONNECTED) {
    while (WiFi.begin(mySSID, myPass) != WL_CONNECTED) {
    Serial << "WiFi connected\n";
    Serial << "Local IP: " << WiFi.localIP() << '\n'; // confirmation only
void loop() {

I accept that the code should check the returned value from WiFi.hostByName() to ensure that the lookup worked correctly.


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