Problem in reading port using QextSerialPort

[cutie.monkey]

hi all, i'm currently doing an application that will send and receive SMS messages using GSM Modem and by sending AT Commands. I used the QextSerialPort class. I connect to the port using this code:

port = new QextSerialPort("COM1"); 
	port->setBaudRate(BAUD19200);   
	port->setFlowControl(FLOW_OFF);
	port->setParity(PAR_NONE);    
	port->setDataBits(DATA_8);   
	port->setStopBits(STOP_2);
	port->open(QIODevice::ReadWrite);

port = new QextSerialPort("COM1"); 
	port->setBaudRate(BAUD19200);   
	port->setFlowControl(FLOW_OFF);
	port->setParity(PAR_NONE);    
	port->setDataBits(DATA_8);   
	port->setStopBits(STOP_2);
	port->open(QIODevice::ReadWrite);

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then send AT COMMANDS:

QString command ="AT\r\n"; //sample command - in Hyperterminal this returns OK
	QByteArray byte;
	byte.clear();
	byte.append(command);
	port->write(byte);
	port->waitForBytesWritten (500);

QString command ="AT\r\n"; //sample command - in Hyperterminal this returns OK
	QByteArray byte;
	byte.clear();
	byte.append(command);
	port->write(byte);
	port->waitForBytesWritten (500);

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then try to read the response:

char buff[1024];
	int numBytes;
	numBytes = port->bytesAvailable(); //always returns -1
	if(numBytes > 0) 
	{
		if(numBytes > 1024)
			 numBytes = 1024;
		int i = port->read(buff, numBytes);
		buff[i] = '\0';
		QString msg = buff;
                qDebug(msg);
		qDebug("bytes available: %d", numBytes);
		qDebug("received: %d", i);
  }

char buff[1024];
	int numBytes;
	numBytes = port->bytesAvailable(); //always returns -1
	if(numBytes > 0) 
	{
		if(numBytes > 1024)
			 numBytes = 1024;
		int i = port->read(buff, numBytes);
		buff[i] = '\0';
		QString msg = buff;
                qDebug(msg);
		qDebug("bytes available: %d", numBytes);
		qDebug("received: %d", i);
  }

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i'm not sure if im doing it right cause when i read the response the bytesAvailable() always returns -1. Is there anybody here can help me or give me a piece of code on how to do it right? thnks in advance...