kannon/classes/Heartbeat.js

const sleep = require('../libs/util.js').sleep;

const EventEmitter = require('events');
const Message = require('./Message.js');

class Heartbeat extends EventEmitter {

    constructor(client) {
        super();
        this.interval = config?.server?.heartbeat || 10000;
        this.client = client;
        this.#listenForPingPong();
        this.#sendPing();
    }

    async #sendPing() {
        if (this.destroyed === true) {
            return;
        }
        if (this.timeout !== undefined) {
            clearTimeout(this.timeout);
        }
        if (this.alive === false) {
            this.emit('timeout');
        }
        if (this.alive === undefined) {
            await sleep(this.interval);
        }
        this.alive = false;
        this.ping = Date.now();
        await new Message('ping').send(this.client);
        await sleep(this.interval);
        this.#sendPing();
    }

    async #listenForPingPong() {
        eventparser.on('ping', () => {
            logger.debug(this.client.getTag() + ' handling event \'ping\', responding with \'pong\'...');
            new Message('pong').send(this.client);
        });
        eventparser.on('pong', () => {
            logger.debug(this.client.getTag() + ' handling event \'pong\'...');
            this.alive = true;
            this.pong = Date.now();
            this.latency = this.pong - this.ping;
            this.emit('network-statistics', {
                ping: this.ping,
                pong: this.pong,
                latency: this.latency
            });
        });
    }

    destroy() {
        this.destroyed = true;
        eventparser.removeAllListeners('ping');
        eventparser.removeAllListeners('pong');
    }

}

module.exports = Heartbeat;