Cannot GET / using node.js + socket.io to connect client to server - node.js

Question

So I am trying to create an indoor location tracker using Bluetooth using the software's node.js and socket.io. I am using a raspberry pi 3 to pickup the RSSI readings and just want the RSSI value from one specific hardware. I have been able to create a connection between my client and server and managed to get the uuid for the specific hardware I want the RSSI value of. However while the connection has been successful I am not getting any of the RSSI values from the pi. Every time I execute the codes below all I get is "Cannot GET / " error whenever I visit my localhost web page.
The following code is what I executed from the pi:
var noble = require('noble');
//replace localhost with your server's IP;
var socket = require('socket.io-client')('http://localhost/scanner');
//replace with your hardware address
var addressToTrack = '7c669d9b2dda';
socket.on('connect', function(){
console.log('connected to server');
});
noble.on('discover', function(peripheral){
if(peripheral.uuid == addressToTrack){
socket.emit('deviceData', {mac: peripheral.uuid, rssi:peripheral.rssi});
}
});
noble.startScanning([], true)
This next code is the code I used to setup my server and how it should receive the information sent from the pi:
var express = require('express');
var app = require('express')();
var http = require('http').Server(app);
var io = require('socket.io')(http);
var scanner = io.of('/scanner');
scanner.on('connection', function(socket) {
console.log('Scanner Connected');
socket.on('message', function(msg) {
//received message from scanner
//do some processing here
});
socket.on('disconnect', function() {
console.log('Scanner Disconnected');
});
});
http.listen(3000, function() {
console.log('listening on *:3000');
});
The following code is taken from https://blog.truthlabs.com/beacon-tracking-with-node-js-and-raspberry-pi-794afa880318 if you're wondering where I am referencing the code from.
I am new to all this so I am trying to understand where the problem is occuring.

Answer 1

You don't have any express route setup for / that's why you're getting: Cannot GET /
Add:
// this should be AFTER socket.io server setup
app.use((req, res) => {
res.send('Hello world');
});
http.listen(3000, function() {
console.log('listening on *:3000');
});
Now every endpoint but socket-io specific endpoints will respond with: hello world
Aside from that, regarding your client side code. You're trying to connect to: http://localhost instead of http://localhost:3000 which the port where your socket.io server is running.