flashsocket on socketio and nodejs not working

I'm trying to get flashsocket working with socket.io but it does not, always going in xhr-polling fallback.

I don't see what I'm doing wrong, if anybody can help.

On server side :

var app = express.createServer(),
io = require('socket.io').listen(app, {
    flashPolicyServer: true,
    transports: ['flashsocket', 'htmlfile', 'xhr-polling', 'jsonp-polling']
});
app.listen(80);

On client side :

...
<script src="/socket.io/socket.io.js"></script>
...
            socket = io.connect();

            socket.on('connect', function(evt) {
                console.log(socket.socket.transport.name);

                onOpen(timeDifference(new Date(), earlierDate), socket.socket.transport.name);
                earlierDate = new Date();
                socket.on('disconnect', function(evt) {
                    onClose(evt);
                });
                socket.on('echo', function(msg) {
                    onEcho(msg);
                });
                socket.on('error', function(evt) {
                    onError(evt);
                });
            });

After that I checked that my browser chrome has flash enabled. I also checked that port 843 and 10843 are listening and responding :

<cross-domain-policy>
    <allow-access-from domain="*" to-ports="*"/>
</cross-domain-policy>

On the server log, only get :

debug - served static content /socket.io.js
debug - client authorized
info  - handshake authorized 14328044138726156
debug - setting request GET /socket.io/1/xhr-polling/14328044138726156?t=1333755740295
debug - setting poll timeout
debug - client authorized for 
debug - clearing poll timeout
debug - xhr-polling writing 1::
debug - set close timeout for client 14328044138726156
debug - setting request GET /socket.io/1/xhr-polling/14328044138726156?t=1333755740299
debug - setting poll timeout
debug - clearing poll timeout
debug - xhr-polling writing 5:::{"name":"echo","args":["transport type : xhr-polling; and socket.id : 14328044138726156"]}
debug - set close timeout for client 14328044138726156
debug - discarding transport
debug - cleared close timeout for client 14328044138726156
debug - setting request GET /socket.io/1/xhr-polling/14328044138726156?t=1333755740303
debug - setting poll timeout
debug - discarding transport
debug - cleared close timeout for client 14328044138726156
debug - clearing poll timeout
debug - xhr-polling writing 8::
debug - set close timeout for client 14328044138726156`

Thanks for you help