Network Time Protocol (NTP) Client

In this example, you will use your Ethernet Shield and your Arduino to query a Network Time Protocol (NTP) server. This way, your Arduino can get the time from the Internet.

Step 1: What You Need?

1 x Arduino Board ( Arduino UNO used in this tutorial) 
1 x Arduino Ethernet Shield

Don't have components? Don't worry. Just click the component's name. 

Step 2: Build Your Circuit.

The Ethernet shield allows you to connect a WizNet Ethernet controller to the Arduino boards via the SPI bus. It uses pins 10, 11, 12, and 13 for the SPI connection to the WizNet. Later models of the Ethernet shield also have an SD Card on board. Digital pin 4 is used to control the slave select pin on the SD card.

The shield should be connected to a network with an ethernet cable. You will need to change the network settings in the program to correspond to your network.

In the above image, the Arduino or Genuino board would be stacked below the Ethernet shield.

Step 3: Upload The Code.

1. Select the Arduino board type: Select Tools >> Board >> Select your correct Arduino board used.

2. Find the port number by accessing device manager on Windows. See the section Port (COM&LPT) and look for an open port named "Arduino Uno (COMxx)". If you are using a different board, you will find a name accordingly. What matters is the xx in COMxx part. In my case, it's COM3. So my port number is 3.

Select the right port: Tools >> Port >> Select the port number.

3. You can find this code in the example of Arduino IDE.

Select File >> Examples >> Ethernet >>  UdpNtpClient

Click press the "upload" button (see the button with right arrow mark).

/* 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 02 Sept 2015
by Arturo Guadalupi This code is in the public domain. */ #include <SPI.h>
#include <Ethernet.h>
#include <EthernetUdp.h> // Enter a MAC address for your controller below.
// Newer Ethernet shields have a MAC address printed on a sticker on the shield
byte mac[] = {
0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED
}; unsigned int localPort = 8888; // local port to listen for UDP packets char timeServer[] = "time.nist.gov"; // 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
EthernetUDP Udp; void setup() {
// Open serial communications and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
} // start Ethernet and UDP
if (Ethernet.begin(mac) == 0) {
Serial.println("Failed to configure Ethernet using DHCP");
// no point in carrying on, so do nothing forevermore:
for (;;)
;
}
Udp.begin(localPort);
} void loop() {
sendNTPpacket(timeServer); // send an NTP packet to a time server // wait to see if a reply is available
delay(1000);
if (Udp.parsePacket()) {
// 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, extract 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 = ");
Serial.println(secsSince1900); // 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:
Serial.println(epoch); // 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)
Serial.print(':');
if (((epoch % 3600) / 60) < 10) {
// In the first 10 minutes of each hour, we'll want a leading '0'
Serial.print('0');
}
Serial.print((epoch % 3600) / 60); // print the minute (3600 equals secs per minute)
Serial.print(':');
if ((epoch % 60) < 10) {
// In the first 10 seconds of each minute, we'll want a leading '0'
Serial.print('0');
}
Serial.println(epoch % 60); // print the second
}
// wait ten seconds before asking for the time again
delay(10000);
Ethernet.maintain();
} // send an NTP request to the time server at the given address
void sendNTPpacket(char* 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);
Udp.endPacket();
}

Download:

Arduino IDE

Sources:https://www.arduino.cc/en/Tutorial/UdpNtpClient   

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