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