Packet reading and modification

I need a program that can decrypt packets and let you modify them before sending, or create new ones to send to the server. Either similar to a proxy like realm relay, or something else.

Has anyone had any success in reading and modifying packets?

People have tried to modify packets and send them off to the server before, it's been tried with damage being dealt, and even health being taken negated to zero, none of which have worked because it's not that simple. I forget which thread it was, but all of this was discussed. Best of luck though!