ntp-time-sync
v0.4.1
Published
Fetches the current time from NTP servers and returns offset information
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ntp-time-sync
Node.JS module to fetch the current time from NTP servers and returns offset information.
:information_source: NTP requires UDP which is not available in a browser context!
Installation
# using Yarn
$ yarn add ntp-time-sync
# using NPM
$ npm install ntp-time-sync
Usage
Consider using the library as a singleton, so that not every call to getTime
fires new NTP packages.
The library itself will manage minimum/maximum poll times.
Several requests to multiple NTP time servers are fired and the responses will be aggregated.
// ES6:
import { NtpTimeSync } from "ntp-time-sync";
// pre-ES6:
// const NtpTimeSync = require("ntp-time-sync").NtpTimeSync;
const timeSync = NtpTimeSync.getInstance();
// request 1
timeSync.getTime().then(function (result) {
console.log("current system time", new Date());
console.log("real time", result.now);
console.log("offset in milliseconds", result.offset);
})
// request 2, will use cached offset from previous request
timeSync.getTime().then(function (result) {
console.log("current system time", new Date());
console.log("real time", result.now);
console.log("offset in milliseconds", result.offset);
})
// ES2017 style
const result = await timeSync.getTime();
console.log("real time", result.now);
<ntpTimeSyncInstance>.getTime()
returns a Promise
object which will eventually be resolved with a object containing the following information:
| Property | Description |
| :--- | :--- |
| now
| Current NTP time ("real time") |
| offset
| Calculated offset between local system time and NTP time |
<ntpTimeSyncInstance>.now()
returns a Date
object containing the correct time for the moment when the function was called.
In contrast to getTime()
, which will return the correct time for the moment the Promise gets resolved.
Options
You can pass custom options to the constructor of NtpTimeSync
or NtpTimeSync.getInstance(options)
.
These will be merged with the following defaults:
const defaultOptions = {
// list of NTP time servers, optionally including a port (defaults to 123)
servers: [
"0.pool.ntp.org",
"1.pool.ntp.org",
"2.pool.ntp.org",
"3.pool.ntp.org"
],
// required amount of valid samples in order to calculate the time
sampleCount: 8,
// amount of time in milliseconds to wait for a single NTP response
replyTimeout: 3000,
// defaults as of RFC5905
ntpDefaults: {
port: 123,
version: 4,
tolerance: 15e-6,
minPoll: 4,
maxPoll: 17,
maxDispersion: 16,
minDispersion: 0.005,
maxDistance: 1,
maxStratum: 16,
precision: -18,
referenceDate: new Date("Jan 01 1900 GMT")
}
};