Reverse proxy websocket IIS

问题:

I would like to use IIS to proxy websocket on windows. So, I set up IIS 8 in Winserver 2012, for reverse proxying a websocket server app. But I don't know how to configure IIS. There is just redirect rules for HTTP and HTTPS, no WS. I would like to have the same thing as apache :

<Location /ws>
ProxyPass ws://127.0.0.1:8080 
ProxyPassReverse ws://127.0.0.1:8080
</Location>

The request ws://127.0.0.1:80/ws will be redirect to ws://127.0.0.1:8080/ws.

Thank you.