Full duplex communication on a TCP socket

I ask this question because...my problem is that when my server (Nios II side) begins to send data continuously (a loop with an 'S' character as end condition) to my client (pc side) I don't succeed in stopping it sending the 'S' character to server....My project is a modified version of simple socket server example...in which I modified the part of SSS_exec_command routine in SSS_Simple_Socket_Server.c file....adding the condition in which if a 'M' character is received ...a loop data sending starts...and if a 'S' character is received this loop data sending SHOULD stop....but I see...this doesn't happen....for all character commands...also led and 7seg display managing commands don't work after the loop starts.