Doctrine in the controller of the socket

[maknaoui]

I have a question , how can i do a modification on the database in the WebSocketService ? i tried to do that :

private $entityManager;
private $clients;
private $container;
public function __construct(EntityManager $entityManager,ContainerInterface $container) 
{
    $this->entityManager = $entityManager;
    $this->container = $container;
    $this->clients = new \SplObjectStorage;
}

but is not working always i have an error