In this tutorial is shown how to get the current time from a Network Time Protocol (NTP) time server using the UDP.
In particular this sketch uses the WiFi Link library on the Arduino Primo.

Use the Arduino IDE 1.8.x  and import the WiFi Link library using the Library Manager.

WiFi Link library



Connect the board to PC

ArduinoPrimo board


Modify the below sketch inserting the name and the password of your network and after upload the code using the Arduino IDE.

Use the Arduino IDE 1.8.x and check that you have already downloaded the corresponding platform (Arduino NRF52 Boards) from the Board Manager.


Udp NTP Client

Get the time from a Network Time Protocol (NTP) time server
Demonstrates use of UDP sendPacket and ReceivePacket
For more on NTP time servers and the messages needed to communicate with them,
see http://en.wikipedia.org/wiki/Network_Time_Protocol

created 4 Sep 2010
by Michael Margolis
modified 9 Apr 2012
by Tom Igoe
modified 10 March 2017
by Sergio Tomasello and Andrea Cannistrá

This code is in the public domain.

#include <WiFiLink.h>
#include <WiFiUdp.h>

int status = WL_IDLE_STATUS;
char ssid[] = "mynetwork"; // your network SSID (name)
char pass[] = "mypassword"; // your network password
int keyIndex = 0; // your network key Index number (needed only for WEP)

unsigned int localPort = 2390; // local port to listen for UDP packets

IPAddress timeServer(129, 6, 15, 28); // time.nist.gov NTP server

const int NTP_PACKET_SIZE = 48; // NTP time stamp is in the first 48 bytes of the message

byte packetBuffer[ NTP_PACKET_SIZE]; //buffer to hold incoming and outgoing packets

// A UDP instance to let us send and receive packets over UDP
WiFiUDP Udp;

void setup()
// Open serial communications and wait for port to open:
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only

//Check if communication with wifi module has been established
if (WiFi.status() == WL_NO_WIFI_MODULE_COMM) {
Serial.println("Communication with WiFi module not established.");
while (true); // don't continue:

// attempt to connect to Wifi network:
while ( status != WL_CONNECTED) {
Serial.print("Attempting to connect to SSID: ");
// Connect to WPA/WPA2 network. Change this line if using open or WEP network:
status = WiFi.begin(ssid, pass);

// wait 10 seconds for connection:

Serial.println("Connected to wifi");

Serial.println("\nStarting connection to server...");

void loop()
sendNTPpacket(timeServer); // send an NTP packet to a time server
// wait to see if a reply is available
if ( Udp.parsePacket() ) {
Serial.println("packet received");
// We've received a packet, read the data from it
Udp.read(packetBuffer, NTP_PACKET_SIZE); // read the packet into the buffer

//the timestamp starts at byte 40 of the received packet and is four bytes,
// or two words, long. First, esxtract the two words:

unsigned long highWord = word(packetBuffer[40], packetBuffer[41]);
unsigned long lowWord = word(packetBuffer[42], packetBuffer[43]);
// combine the four bytes (two words) into a long integer
// this is NTP time (seconds since Jan 1 1900):
unsigned long secsSince1900 = highWord << 16 | lowWord;
Serial.print("Seconds since Jan 1 1900 = " );

// now convert NTP time into everyday time:
Serial.print("Unix time = ");
// Unix time starts on Jan 1 1970. In seconds, that's 2208988800:
const unsigned long seventyYears = 2208988800UL;
// subtract seventy years:
unsigned long epoch = secsSince1900 - seventyYears;
// print Unix time:

// print the hour, minute and second:
Serial.print("The UTC time is "); // UTC is the time at Greenwich Meridian (GMT)
Serial.print((epoch % 86400L) / 3600); // print the hour (86400 equals secs per day)
if ( ((epoch % 3600) / 60) < 10 ) {
// In the first 10 minutes of each hour, we'll want a leading '0'
Serial.print((epoch % 3600) / 60); // print the minute (3600 equals secs per minute)
if ( (epoch % 60) < 10 ) {
// In the first 10 seconds of each minute, we'll want a leading '0'
Serial.println(epoch % 60); // print the second
// wait ten seconds before asking for the time again

// send an NTP request to the time server at the given address
unsigned long sendNTPpacket(IPAddress& address)
// set all bytes in the buffer to 0
memset(packetBuffer, 0, NTP_PACKET_SIZE);
// Initialize values needed to form NTP request
// (see URL above for details on the packets)
packetBuffer[0] = 0b11100011; // LI, Version, Mode
packetBuffer[1] = 0; // Stratum, or type of clock
packetBuffer[2] = 6; // Polling Interval
packetBuffer[3] = 0xEC; // Peer Clock Precision
// 8 bytes of zero for Root Delay & Root Dispersion
packetBuffer[12] = 49;
packetBuffer[13] = 0x4E;
packetBuffer[14] = 49;
packetBuffer[15] = 52;


// all NTP fields have been given values, now
// you can send a packet requesting a timestamp:
Udp.beginPacket(address, 123); //NTP requests are to port 123
Udp.write(packetBuffer, NTP_PACKET_SIZE);

void printWifiStatus() {
// print the SSID of the network you're attached to:
Serial.print("SSID: ");

// print your WiFi shield's IP address:
IPAddress ip = WiFi.localIP();
Serial.print("IP Address: ");

// print the received signal strength:
long rssi = WiFi.RSSI();
Serial.print("signal strength (RSSI):");
Serial.println(" dBm");


Open the Serial Monitor and look the current time:

WiFiUdpNtpClient for Primo