Dunno about vb6 but for c++ reference you can read source antihack made by f1x from rz. Even there's one thread about gameguard free version by pink0f and how to inject it with ollydbg. Or you can try read source antihack made for other game such MUguard,rajanms once you get the basic idea you might develop one for yourself even if you fail you will learn something new
word of my mentor semutputih
I suggest you spend time developing packet intercept since the core problem is mapserver once you fix it that will give you time to develop client protection. I saw one posting SS with winpcap and one ss made by another pserver
