Example of using tls-json + express to create a master server listing service.

master.js

const fs = require('fs')
const express = require('express')
const config = require('config')
const TLSServer = require('tls-json').Server
const Router = require('express-promise-router')
const servers = require('../servers')

const app = express()
app.use(express.json())
app.use(express.urlencoded({ extended: true }))

// game instances connected to the master server
const clients = new Map()

let instanceListing = []
let invalidateCache = false
let cacheTimestamp = Date.now()

// rebuilds the public-facing server list
const rebuildListing = function () {
    const now = Date.now()
    // cache logic: don't rebuild the list unless it has been 500 ms
    if (now > cacheTimestamp + 500 || invalidateCache) {
        cacheTimestamp = now
        invalidateCache = false

        instanceListing = []
        clients.forEach(client => {
            const listing = {}
            for (prop in client) {
                if (prop !== 'socket') {
                    listing[prop] = client[prop]
                }
            }
            instanceListing.push(listing)
        })
    }
}

const server = new TLSServer({
    options: {
        key: fs.readFileSync(config.API_KEY),
        cert: fs.readFileSync(config.API_CERT)
    },
    password: config.API_PASSWORD
})

server.on('authenticated', (id, socket) => {
    let ip = socket.remoteAddress
    if (ip.startsWith("::ffff:")) {
        ip = ip.slice(7)
    }
    const subdomain = servers.byIp(ip)
    // create the initial listing, id, socket, ip, subdomain
    clients.set(id, { id, socket, ip, subdomain })
})

server.on('close', id => {
    invalidateCache = true
    clients.delete(id)
})

server.on('error', (id, err) => {
    console.log(`client(${id})::error::${err}`)
})

server.on('message', (id, message) => {
    if (message.type === 'list') {
        // copy the submitted listing to our records
        Object.assign(clients.get(id), message.listing)
    }
})

server.on('request', (id, req, res) => { })

server.listen(config.MASTER_API_PORT, () => {
    console.log(`MASTER API listening on ${config.MASTER_API_PORT}`)
})

const router = new Router()

// public server listing
router.get('/servers', async (req, res) => {
    rebuildListing()
    res.send(instanceListing)
})

app.use(router)

app.listen(7999, () => {
    console.log(`MASTER HTTP listening on 7999`)
})