To verify the source of the sight that I am receiving packets from, is there a way to alter the tcp/ip ACK packet to "packets received minus one"? My objective is to verify that the computer I am connected to is no a spoofed machine. If the ACK packet is altered, my understanding is that a "real" computer will resend the packets / if it’s a spoofed ip, the computer will simply drop the ACK as trash. This is for a class project which I’ll admit parts of this is over my head at this point. But how else to learn.

Hi, I’m sure there is a simple change that could be made for this – but I don’t know what it is!  Are you using uIP?  If you cannot find the relevant line in the source files then you might like to ask Adam Dunkels.  His sight is more likely to be of use. Regards.