Dull doesn't natively support the Web-Socket protocol. But you can use an external program along with a Dull managed tunnel
For example, see https://github.com/novnc/websockify. Websockify can provide a websocket data interface to an underlying raw TCP server communications stream. Websockify works best with Linux, Ubuntu for Windows, a Ubuntu virtual machine, or a remote ubuntu server might be required. There might be a way to compile a native windows executable.
There is no guide that demonstrates use of this kind of duct.