Using TCP Receive for interaction with c++ app

I create model where I create "tcp receive" & "tcp send" blocks. Between them I insert sin-block. After I connect to receive element I send single value. But when I try read data I receive continuos last value. I set model time to "inf". When I send to model new value I receive new answer but also read this value continuos, whithout end. How can I build interaction with model on trigger base model:

 cpp -> send data -> model receive new data -> send new answer -> wait for new input data

Thank you, Regards