App.js file that runs the server.

socket-io-tutorial-app.js

var express = require('express');
var path = require('path');
var app = express();
var server = require('http').Server(app);
var io = require('socket.io')(server);
var port = 8080;

app.use(express.static(path.join(__dirname, "public")));


io.on('connection', function(socket) {
  console.log('new connection made'); // send to the output

  socket.emit('message-from-server', {
    greeting: 'Hello from Server'
  });

  socket.on('message-from-client', function(msg) {
    console.log(msg);
    socket.broadcast.emit('broadcast-to-client',{ message: msg.message });
  });
  
});

server.listen(port, function() {
  console.log("Listening on port " + port);
});