why GSM modem is not responding to program but responding to hyperterminal or docklight?

Question

EDITED:

Im developing SMS application in java for reading SMS.Im sending AT commands to GSM mode for sending an SMS,messages is sending successfully ,but im not getting any response from the modem.If i send the AT commands through Hyperterminal im getting the response.Whats the exact problem?

            InputStream inputStream;
            OutputStream out;


            this.inputStream = serialPort.getInputStream();
            this.out = serialPort.getOutputStream();
            out.write(("AT"+"\r").getBytes());
            try {
                Thread.sleep(1500);
            } catch (InterruptedException ex) {
                Logger.getLogger(MainClass.class.getName()).log(Level.SEVERE, null, ex);
            }
            out.write(("AT+CMGF=1"+"\r").getBytes());
            try {
                Thread.sleep(1500);
            } catch (InterruptedException ex) {
                Logger.getLogger(MainClass.class.getName()).log(Level.SEVERE, null, ex);
            }
            out.write(("AT+CMGS=\""+"+91xxxxxxxxxx"+"\""+"\r").getBytes());
            try {
                Thread.sleep(1500);
            } catch (InterruptedException ex) {
                Logger.getLogger(MainClass.class.getName()).log(Level.SEVERE, null, ex);
            }
            out.write(("TEST "+cntrlZ).getBytes());
            try {
                Thread.sleep(1500);
            } catch (InterruptedException ex) {
                Logger.getLogger(MainClass.class.getName()).log(Level.SEVERE, null, ex);
            }


 //Im using SerialPortEventListener to  read the input from modem
int a = inputStream.available();
System.out.println(inputStream.available() + "  BYTES AVAILABLE ");
inputStream.read(readBuffer, 0, a);

I also tried to read after sending each AT commands,but im not getting anything as a response from the modem.

Answer 1

Issues receving in RXTX

After setting the flow control for the serial port its working fine.

serialPort.setFlowControlMode(SerialPort.FLOWCONTROL_RTSCTS_IN |    SerialPort.FLOWCONTROL_RTSCTS_OUT);