Socket.io 404 Not Found

For some reason I keep getting "http://127.0.0.1:3000/socket.io/socket.io.js" 404 not found when I look under chrome developer tools network. I have spent over an hour trying to understand why this isn't working because it was working fine before and I didn't think I changed anything.

Server:

var express = require('express'),
    session = require('express-session');

var app = express();

var server = require('http').Server(app);
var io = require('socket.io')(server);
var MongoStore = require('connect-mongo')(session);

var sessionMiddleware = session({
    resave: false,
    saveUninitialized: false,
    secret: 'secret',
    store: new MongoStore({url: "mongodb://localhost:27017/database"})
});

app.use(sessionMiddleware);



io.use(sessionMiddleware, function(socket, next) {
    sessionMiddleware(socket.request, socket.request.res, next);
});

io.sockets.on('connection', function (socket) {
    console.log("Socket connected");
});

app.set('view engine', 'pug');
app.use(express.static(__dirname + '/public'));

app.get('/', function(req, res) {
   res.render('index');
});

app.listen(3000);
console.log('listening');

Pug File:

html
    head
        script(src="http://127.0.0.1:3000/socket.io/socket.io.js")
        script(type='text/javascript', src='../javascripts/chat.js')
    body

Client javascript:

try {
    var socket = io.connect('http://127.0.0.1:3000');

} catch(e) {
    console.log(e);
}