Well?....
You can change packets if you want, edit packets, create packets, etc.... and have them sent to the DO servers, But DO servers check the packets to ensure they're correct, and do other types of checks on what is sent to/from their servers. For the most part, Its kind of useless if you're wanting to /bug the game/, every now and again a bug is found, and Charlie is easy to use to replicate the bug (such as a few of the old old bugs).
As you can imagine, Most games/servers, etc validate packets, so it isn't super super easy to inject fake data and such, Go download it, and have a play about with it, you got nothing to lose, but if you had to ask what Charlie is; the odds are, you've got nothing to gain as-well other than a little experience.
regards
Tw
Edit:
I'd imagine DO /may/ log false/dodgy packets, So if you're playing about, maybe an idea is to test while logged into a nub account. Lol
Edit 2:
Ohh, you' should readup on base64 also