/*

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
updated for the ESP8266 12 Apr 2015
by Ivan Grokhotkov

This code is in the public domain.

*/

#include <ESP8266WiFi.h>
#include <WiFiUdp.h>

char ssid[] = "mySSID"; // your network SSID (name)
char pass[] = "myPassword"; // your network password


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

/* Don't hardwire the IP address or we won't get the benefits of the pool.
* Lookup the IP address for the host name instead */
//IPAddress timeServer(129, 6, 15, 28); // time.nist.gov NTP server
IPAddress timeServerIP; // time.nist.gov NTP server address
const char* ntpServerName = "time.nist.gov";

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()
{
Serial.begin(115200);
Serial.println();
Serial.println();

// We start by connecting to a WiFi network
Serial.print("Connecting to ");
Serial.println(ssid);
WiFi.begin(ssid, pass);

while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");

Serial.println("WiFi connected");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());

Serial.println("Starting UDP");
udp.begin(localPort);
Serial.print("Local port: ");
Serial.println(udp.localPort());
}

void loop()
{
//get a random server from the pool
WiFi.hostByName(ntpServerName, timeServerIP);

sendNTPpacket(timeServerIP); // send an NTP packet to a time server
// wait to see if a reply is available
delay(1000);

int cb = udp.parsePacket();
if (!cb) {
Serial.println("no packet yet");
}
else {
Serial.print("packet received, length=");
Serial.println(cb);
// 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 = " );
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);
}

// send an NTP request to the time server at the given address
unsigned long sendNTPpacket(IPAddress& address)
{
Serial.println("sending NTP packet...");
// 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();
}