Are Spam requests effective in multiple threads?

[nwndm]

I was just wondering, if I put spamming requests in multiple threads that occur in parallel and only spam for like 5 seconds, but at 5 millisecond intervals will the server take them or reject a good portion of them? OR is there some bottleneck on the server or client side network that I may hit? Would a single thread be about as effective then, if the server rejects a portion of the request sent out anyways?

Thanks