Sending message to client with Web Sockets

I'm using https://github.com/orchidsoftware/web-socket in my laravel project and I want to send messages to clients connected.

So far I've followed the README and got the server up and running - I get the alert "The connection is established.".

But when I try to send a message to the client, nothing happens. I've created a sendMessageToAll function and tried to call it both from onOpen and from another controller:

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

public function sendMessageToAll($msg){
    foreach ($this->clients as $client) {
        $client->send($msg);
    }
}

And from another controller:

public function test() {
    $ws = new WebSocketClass();
    $ws->sendMessageToAll("testing");
}

Is there something I'm missing in order to get it up and running?

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