I do not know if you have the processing time, but I once did a critical process by returning what I got to the sender and waiting for the sender to send an unique string to say "you got it right". This is fairly simple to implement, but again, you need the time to return the data (can be done simulatanously on some systems) and wait for the accept signal. I know taht this is a very pedestrian solution, but it is safe and it works.

Have fun,

Erik