Update SendPacket.cc

Added message exchange between nodes using DH secret key pairwise - 1 round as of now

Left over:
1. after receiving the messages and decrypting it using the shared secret key, each node will exor adjacent bits received (sender will invert it).
2. Again they share this ex-ored bit to every other node.(broadcast)
3. Then after receiving all the exor bits - they compute again teh exor of these bits which the first message bit.