TCP Slave responses

Question

With the example from the jamod page I am trying to create a TCP Slave, which would accept WriteMultipleRegisters (fc16) requests and send appropriate responses. code:

//1. Prepare a process image

for (int i = 0; i < 200; i++)
    spi.addRegister(new SimpleRegister(0));

ModbusCoupler.getReference().setProcessImage(spi);
ModbusCoupler.getReference().setMaster(false);
ModbusCoupler.getReference().setUnitID(254);

//3. create a listener with 3 threads in pool
if (Modbus.debug) System.out.println("Listening...");

listener = new ModbusTCPListener(1, addr);
listener.setPort(port);   
listener.start(); 

With this code I am able to get requests (write in these 200 registers) but I am wondering why it didn't send any responses?