Why node.js requires an upgrade while trying to run an application on the localhost?

Question

When I try to run my node.js application on a localhost server, it does not run and demands a required upgrade. I have tried to run the code but I get the following error:

Answer 1

You need to combine your WebSocket based server and static html generator Express. For example

var express = require('express')
var expressWs = require('express-ws')

var app = express()
expressWs(app)

app.ws('/echo', (ws, req) => {

    ws.on('connection', function (connection) {
        //...
    })

    ws.on('close', function () {
        //...
    })
})

app.use(express.static('public'))
app.listen(3000, function () {
    console.log('Example app listening on port 3000!')
})

In client code

var ws = new WebSocket('ws://localhost:3000/echo');
ws.onmessage=function(event){
   document.getElementById("result").value=event.data;
}