socket io not found - 404

I ran into this error when following a tutorial about creating a chat service. Here is the code: (most of it is automatically generated)

var port = normalizePort(process.env.PORT || '3000');
app.set('port', port);

/**
 * Create HTTP server.
 */

var server = http.createServer(app);

/**
 * Listen on provided port, on all network interfaces.
 */

var io = require('socket.io').listen(app.listen(port));
io.sockets.on('connection', function (socket) {
    socket.emit('message', { message: 'welcome to the chat' });
    socket.on('send', function (data) {
        io.sockets.emit('message', data);
    });
});

Client side:

script(src='/javascripts/chat.js')
script(src='/http://ift.tt/1aeIZU4')

Do I actually have to manually put socket.io.js into the folder? I don't get it...