同步ntp服务器时间

hgmyaoming

time_t getNtpTime()
    {
      while (Udp.parsePacket() > 0) ; // discard any previously received packets
      Serial.println("Transmit NTP Request");
      sendNTPpacket(timeServer);
      uint32_t beginWait = millis();
      while (millis() - beginWait < 1500) {
        int size = Udp.parsePacket();
        if (size >= NTP_PACKET_SIZE) {
          Serial.println("Receive NTP Response");
          Udp.read(packetBuffer, NTP_PACKET_SIZE);  // read packet into the buffer
          unsigned long secsSince1900;
          // convert four bytes starting at location 40 to a long integer
          secsSince1900 =  (unsigned long)packetBuffer[40] << 24;
          secsSince1900 |= (unsigned long)packetBuffer[41] << 16;
          secsSince1900 |= (unsigned long)packetBuffer[42] << 8;
          secsSince1900 |= (unsigned long)packetBuffer[43];
          return secsSince1900 - 2208988800UL + timeZone * SECS_PER_HOUR;
        }
      }

这是获取时间的函数，具体是什么算法看不太明白，望多多指教！