Tasmota/lib/lib_div/ArduinoNTPd/NTPServer.cpp

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/*
* File: NTPServer.cpp
* Description:
* NTP server implementation.
* Author: Mooneer Salem <mooneer@gmail.com>
* License: New BSD License
*/
#include <WiFiUdp.h>
#include "NTPPacket.h"
#include "NTPServer.h"
#define NTP_PORT 123
#define NTP_TIMESTAMP_DIFF (2208988800) // 1900 to 1970 in seconds
bool NtpServer::beginListening()
{
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if (timeServerPort_.begin(NTP_PORT)){
return true;
}
return false;
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}
bool NtpServer::processOneRequest(uint32_t utc, uint32_t millisecs)
{
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// millisecs is millis() at the time of the last iTOW reception, where iTOW%1000 == 0
uint32_t refMillis = millis()-millisecs;
if (refMillis>999){
utc++;
refMillis = refMillis%1000;
}
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bool processed = false;
int packetDataSize = timeServerPort_.parsePacket();
if (packetDataSize && packetDataSize >= NtpPacket::PACKET_SIZE)
{
// We need the time we've received the packet in our response.
uint32_t recvSecs = utc + NTP_TIMESTAMP_DIFF;
uint64_t recvFract64 = refMillis;
recvFract64 <<= 32;
recvFract64 /= 1000;
uint32_t recvFract = recvFract64 & 0xffffffff;
// is equal to:
// uint32_t recvFract = (double)(refMillis)/0.00000023283064365386963;
// Received what is probably an NTP packet. Read it in and verify
// that it's legit.
NtpPacket packet;
timeServerPort_.read((char*)&packet, NtpPacket::PACKET_SIZE);
// TODO: verify packet.
// Populate response.
packet.swapEndian();
packet.leapIndicator(0);
packet.versionNumber(4);
packet.mode(4);
packet.stratum = 1; // >1 will lead to misinterpretation of refId
packet.poll = 10; // 6-10 per RFC 5905.
packet.precision = -21; // ~0.5 microsecond precision.
packet.rootDelay = 100 * (0xFFFF / 1000); //~100 milliseconds
packet.rootDispersion = 50 * (0xFFFF / 1000);; //~50 millisecond dispersion
packet.referenceId[0] = 'G';
packet.referenceId[1] = 'P';
packet.referenceId[2] = 'S';
packet.referenceId[3] = 0;
packet.referenceTimestampSeconds = recvSecs;
packet.referenceTimestampFraction = 0; // the "click" of the GPS
packet.originTimestampSeconds = packet.transmitTimestampSeconds;
packet.originTimestampFraction = packet.transmitTimestampFraction;
packet.receiveTimestampSeconds = recvSecs;
packet.receiveTimestampFraction = recvFract;
// ...and the transmit time.
// the latency has been between 135 and 175 microseconds in internal testing, so we harcode 150
uint32_t transFract = recvFract+(150*(10^3)/(2^32)); // microsec/((10^3)/(2^32))
if (recvFract>transFract){
recvSecs++; //overflow
}
packet.transmitTimestampSeconds = recvSecs;
packet.transmitTimestampFraction = transFract;
// Now transmit the response to the client.
packet.swapEndian();
timeServerPort_.beginPacket(timeServerPort_.remoteIP(), timeServerPort_.remotePort());
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timeServerPort_.write((const uint8_t *)packet.packet(), NtpPacket::PACKET_SIZE);
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timeServerPort_.endPacket();
processed = true;
}
return processed;
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}