Use base64 encode/ decode on client and server. All the web browsers with WebSockets have window.atob (base64 decode) and window.btoa (base64 encode). The WebSockets server has base64 libraries.
To transfer binary data, you would be working with wsproxy included with no VNC that is a web based VNC client.
The wsproxy is a WebSockets to generic TCP sockets proxy. The base64 encodes/decodes all traffic to/from the browser. Use it to connect from a WebSockets capable browser to any type of TCP port.