I have 2 PC. One is Xp(sp2) System, One is Win7(Ultimate). They in Same Lan. Test1: Xp send (1000byte) Udp packet to Win7. It is Success. Win7 send (1000byte) Udp packet to Xp, It is Success. Test2: Xp send (1600byte) Udp packet to Win7. It is Failed. Win7 send (1600byte) Udp packet to Xp...