Transport-agnostic client-server clock synchronization
npm install clocksyTransport-agnostic client-server clock synchronization.
* Simple algorithm: timestamp at the client, timestamp at the server and send back, measure round-trip time, estimate server time and apply an IIR filter to improve accuracy over time.
* Transport-agnostic: use it on top of your own transport layer: HTTP, WebSockets, MQTT, whatever.
* Simple implementation: since it leaves transport on the user's hands, it is exactly 5 LOCs for the server, ~70 for the client.
* Automatic requests, typically converging to < 10 ms in a few iterations.
* Automatic background tab detection: Chrome goes bonkers with –sorry, optimizes– timers on background tabs, interfering with clocksy's algorithm. Automatic clock updates are switched off while a tab is hidden.
``
$ npm install --save clocksy
and return the result to the client as fast as you can:
`js
import { ClocksyServer } from 'clocksy'; // const { ClocksyServer } = require('clocksy');
const clocksy = new ClocksyServer();
// ...
socket.on('MSG', msg => {
const { type, data } = msg;
if (type === 'CLOCKSY') {
socket.emit('MSG', {
type: 'CLOCKSY',
data: clocksy.processRequest(data),
});
return;
}
// ...
})
`
$3
Enable/disable automatic requests by using ClocksyServer.start|stop()
and pass any response you get from the server to Clocksy, as fast as you can:
`js
import { ClocksyClient } from 'clocksy'; // const { ClocksyClient } = require('clocksy');
const socket = socketio.connect(url);
const clocksy = new ClocksyClient({
sendRequest: req => socket.emit('MSG', { type: 'CLOCKSY', data: req }),
// Other parameters and their default values:
// alpha: 0.2, // higher levels accelerate convergence but decrease accuracy
// updatePeriod: 10000, // [ms] how often should Clocksy estimate clock error
});
socket.on('connect', () => clocksy.start());
socket.on('disconnect', () => clocksy.stop());
socket.on('MSG', msg => {
const { type, data } = msg;
if (type === 'CLOCKSY') {
const tDelta = clocksy.processResponse(data);
// tDelta is the estimated server time minus the local time.
// Use this delta for whatever purpose you want, e.g.
// correcting the local time for graphs or changing the timestamps
// of data downloaded from the server...
// If you don't need the delta immediately, you can also obtain it later
// calling clocksy.getDelta())
return;
}
});
``* timesync: provides more functionalities, but is apparently more complex.
Copyright (c) Guillermo Grau Panea 2016
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