websockets connections fail with apache and Ratchet

I wrote a php websockets server using the library Ratchet that I call with javascript using the websocket object.

Everything worked perfectly locally but it was impossible to run my project on my Debian server under apache.

To enable websocket connections I read that I have to use mod_proxy_wstunnel module. So I rewrite my apache conf for my subdomain api.domain.com like this:

<VirtualHost *:80>
        ServerAdmin admin@admin.admin
        DocumentRoot /var/www/api.domain.com
        ServerName api.domain.com

        # Enable Websocket connections on port 8888
        ProxyPass "/wss/homews/" "ws://api.domain.com:8888/"

        <Directory /var/www/api.domain.com>
                Options FollowSymLinks
                AllowOverride All
                Order allow,deny
                Allow from all
                Satisfy all
        </Directory>
</VirtualHost>

Then I call my php script with this code insight that start Ratchet websocket server:

// ...
// Some code ...
$app = new Ratchet\App('localhost', 8888);
$app->route('/wss/homews/', $myClass, array('*'));
$app->run();

Then when I try to connect to it on the javascript client side with the url ws://api.domain.com:8888/wss/homews/ I always get Error in connection establishment: net::ERR_CONNECTION_TIMED_OUT.

Do you have any ideas how I could debug this type of error ? Are there any logs on apache showing a bad configuration?

from websockets connections fail with apache and Ratchet