在客户端断开连接之前，Websocket不发送消息

Question

我正在使用PHP库Ratchet学习WebSocket。但是我从客户端/浏览器发送消息时遇到问题。我已经尝试过使用chrome和firefox。

直到我通过关闭选项卡或刷新浏览器来断开客户端的连接，消息才会发送到服务器。

更新：我的服务器使用启用了Firewalld的Centos 7。

关闭浏览器选项卡后，服务器输出如下：

Connection 73 sending message "tes" to 1 other connection
Connection 73 has disconnected

这是JavaScript代码：

conn = new WebSocket('ws://websocket.develop.local:8080');
            conn.onopen = function(e) {
                console.log("Connection established!");
            };

            conn.onmessage = function(e) {
                console.log('ada message');
                console.log(e.data);
            };
            conn.onerror = function(e) {
               console.log("WebSocket Error: " , e);
               //Custom function for handling errors
               //handleErrors(e);
            };
            function sendMessage(){
                    var message = document.getElementById("pesan").value;
                    conn.send(message);
                    console.log('Sending message: ' + message);
            };

这是PHP代码（我是从Ratchet文档中获得的）：

    <?php
namespace MyApp;
use Ratchet\MessageComponentInterface;
use Ratchet\ConnectionInterface;

class Chat implements MessageComponentInterface {
    protected $clients;

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

    public function onOpen(ConnectionInterface $conn) {
        // Store the new connection to send messages to later
        $this->clients->attach($conn);

        echo "New connection! ({$conn->resourceId})\n";
    }

    public function onMessage(ConnectionInterface $from, $msg) {
        $numRecv = count($this->clients) - 1;
        echo sprintf('Connection %d sending message "%s" to %d other connection%s' . "\n"
            , $from->resourceId, $msg, $numRecv, $numRecv == 1 ? '' : 's');

        foreach ($this->clients as $client) {
            if ($from !== $client) {
                // The sender is not the receiver, send to each client connected
                $client->send($msg);
            }
        }
    }

    public function onClose(ConnectionInterface $conn) {
        // The connection is closed, remove it, as we can no longer send it messages
        $this->clients->detach($conn);

        echo "Connection {$conn->resourceId} has disconnected\n";
    }

    public function onError(ConnectionInterface $conn, \Exception $e) {
        echo "An error has occurred: {$e->getMessage()}\n";

        $conn->close();
    }
}