I'm not clear on what you want to do. Do you want to fuzz a VNC server? There are some ways you can do that. Try to find docs online that detail the protocol o

I'm not clear on what you want to do. Do you want to fuzz a VNC server? There are some ways you can do that. Try to find docs online that detail the protocol or read the source of open-source VNC servers to infer the protocol. You can then use some existing tools to generate some traffic (peach or scapy, among many others). I'm not a fan of Peach for a few reasons, but some people use it. In general, you'd want to cover edge cases of inputs being parsed. Signed/unsigned edges for integers, strings of various lengths with common bad input patterns, unordered type-length-value pairs, etc and etc. Try finding past vulnerabilities in the server you're trying to break and see where others found holes. Check the changelog. Try instrumenting an existing client.