I'm trying to create a dll for another application that I didn't build that only accepts unmanaged C/C++ dlls. This is for hooking into a game and pinging clients that connect to the game (the application I didn't build). I've been looking at tons and tons of stuff on google, but I can't find anything that seems to be the holy grail.

What I'm chiefly concerned about is this:

Do I use ICMP or TCP for this? Is it possible to spam a client with ping requests and therefore be seen as a threat, or to accidentally do denial of service sort of attack on clients using ICMP?

Any help would be appreciated. (I'm still looking at how to design the program at the moment, and looking for any roadblocks or obstacles)

P.S. I posted this in Yahoo answers, but it doesn't look like I'll be getting any answers there (which doesn't surprise me), so I thought I'd try here. (Oh, and I added a few details for this post)