websocket-proxy.cjs

const http = require('http')
const express = require('express')
const WebSocket = require('ws')

const app = express()
const server = http.createServer(app)
const wss = new WebSocket.Server({ server })

const deviceUrl = 'ws://192.168.1.99/timerws'
const deviceSocket = new WebSocket(deviceUrl)
const browserClients = new Set()

deviceSocket.on('message', msg => {
  for (const client of browserClients) {
    if (client.readyState === WebSocket.OPEN) {
      client.send(msg)
    }
  }
})

wss.on('connection', browserSocket => {
  console.log('Connection connected')
  browserClients.add(browserSocket)

  browserSocket.on('message', msg => {
    if (deviceSocket.readyState === WebSocket.OPEN) {
      deviceSocket.send(msg)
    }
  })

  browserSocket.on('close', () => {
    browserClients.delete(browserSocket)
    if (!browserClients.size && deviceSocket.readyState === WebSocket.OPEN) {
      deviceSocket.close()
    }
  })
})

server.listen(4326, () => console.log('Proxy server on port 4326'))