socket.io not receiving messages on server

server sided code

const express = require('express')
const app = express()
const server = require('http').Server(app)
const io = require('socket.io')(server)
io.once('connection', function (socket) {
  console.log(`New connection`)
  socket.emit('hello', 'hello from the server')
  socket.on('clientData', (data) => {
    console.log(data)
  })
})
server.listen(3000, () => {
  console.log(`Server started: http://localhost:${port}`)
})

Client side code:

var socket = io()
var hello = 'Hello server'
socket.on('connection', function() {
    console.log('established connection')
    socket.emit('clientData', hello)
})
socket.on('hello', function(data) {
  console.log(data)
})

When run the client doesnt emit the 'clientData' for some reason, what am I doing wrong.

via Satonamo