Ping dll for game

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)

Ping naturally implies ICMP protocol which may be just disabled/prohibited on client's side.

So this is the game framework who must take care about exchanging certain watchdog packets to see if the client is still alive.

If you have an actual connection between 2 machines, you can piggyback latency calculations on top of your normal traffic. rather than use an actual ping system.

Thanks for the responses. Piggybacking off the normal traffic seems to make since. I wondered if ICMP would really be used in such a situation, but now that doesn't seem likely.

Why not contact the game manufacturer and ask if there is any extensibility provisions (i.e. SDK) for the game?