Laravel 5 - Class 'DB' not found

I have ChatController located in app/http/controllers like so:

namespace App\Http\Controllers;

use App\Http\Controllers\Controller;

use Ratchet\MessageComponentInterface;
use Ratchet\ConnectionInterface;
use DB;

class ChatController extends Controller implements MessageComponentInterface {

    protected $clients;

    function __construct() {
        $this->clients = new \SplObjectStorage;
    }

    public function onOpen(ConnectionInterface $conn) 
    {
        $this->clients->attach($conn);
    }

    public function onMessage(ConnectionInterface $conn, $msg) 
    {
        foreach ($this->clients as $client) 
        {
            if ($client !== $conn )
                $client->send($msg); 

            DB::table('messages')->insert(
                ['message' => $msg]
            );
        }
    }

    public function onClose(ConnectionInterface $conn) 
    {
        $this->clients->detach($conn);
    }

    public function onError(ConnectionInterface $conn, \Exception $e) 
    {
        echo 'the following error occured: ' . $e->getMessage();
        $conn->close();
    }

}

And I have chatserver.php file in the root like so:

<?php
require  'vendor/autoload.php';

use Ratchet\Server\IoServer;
use Ratchet\Http\HttpServer;
use Ratchet\WebSocket\WsServer;
use App\Http\Controllers\ChatController;


$server = IoServer::factory(
    new HttpServer(
        new WsServer(
            new ChatController()
        )
    ),
    8080
);

$server->run();

If I remove

DB::table('messages')->insert(
                    ['message' => $msg]
                );

from the ChatController and start chatserver.php it works, but if I don't remove it then the server starts but as soon as I send a message I get this error:

Fatal error: Uncaught Error: Class 'DB' not found in C:\wamp\www\laraveltesting\app\Http\Controllers\ChatController.php:31

Why won't it use DB? I am extending the laravel controller.

via Chebli Mohamed