Ofmeet cannot start conference

Hi all,

I've just installed openfire 3.10 and ofmeet plugin.

Tried to start a conference but it halt in "your  conference is currently being created" session when i press the invite others.

Open the logs and I find this :

2015.10.20 13:35:54 XMPPServlet - An error occurred while attempting to create a web socket (USERNAME: sandy RESOURCE: ofmeet3354 ) :

Do you have any clue about the error ?

Thanks

Sandy