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.
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.