I was using Keil Tiny TCP/IP Stack on 2x MCB167-NET board configuration as clients, connecting to the PC that acts as a server. No communications problem when there is only communication between either board and PC. However, if the 2x boards were to sent information simulateously, most of the time, one of the boards will have communication error. One situation was when the PC closes all sockets, occasionally, one system still remains active, i.e. socket status active and connected. Does anybody ever tried setting up a network of systems and faced any problems? The documention mentions that TCP/IP stack has restriction like "Only one active TCP session at the same time". May Keil or anybody kindly enough to elaborate the meaning? Many thanks in advance for any replies!