QextSerialPort port->write Problem

I seem to be having difficulty using the PortListener class. If I write to a connected port directly everything is fine. If I write via a public or private function using identical code I get an error:

â€œApplication.exe has encountered a problem and needs to close.â€

It seems a bizarre problem so I must be missing something really simple. My apologies in advance if this is the case. I have cut the code down to a minimal case that still generates the problem.

Code:

MainWindow::MainWindow(QWidget *parent): QMainWindow(parent){
    QWidget *w = new QWidget(this);
    scPtr = new Session ();
    QString portName = scPtr->enumerate();
    if (portName == "NULL"){
        qDebug() << "Serial Device NOT FOUND portName = " << portName;
        int i = QMessageBox::warning(this,tr("Connection"),tr("No SerialDevices detected."),QMessageBox::Cancel);
    }else{ qDebug() << "SerialDevice Found. portName = " << portName; }
    PortListener *listener = new PortListener(portName); 
 
//============ below does not work?===============
    clickTEST0();
 
//============ below works======================
    QByteArray ba;
    ba.resize(3);
    ba[0] = 254 ;               
    ba[1] = 1;       
    ba[2] = 255;
    int i = listener->port->write(ba,ba.length());
}
 
void MainWindow::clickTEST0() {
    QByteArray ba;
    ba.resize(3);
    ba[0] = 254 ;               
    ba[1] = 1; 
    ba[2] = 255;
    int i = listener->port->write(ba,ba.length());
}
 
Session::Session(){} 
 
QString Session::enumerate(){
    QList<QextPortInfo> ports = QextSerialEnumerator::getPorts();
    int tempport = 9999;
    QString tempportname = "NULL";
    QString tempfriendname = "NULL";
    QString qstr;               
    int portsize = 0;
    for (int i = 0; i < ports.size(); i++) {
        portsize++;
        qstr = ports.at(i).enumName;
        if (qstr ==  SerialDeviceString) {
            tempport = i;
            tempportname = ports.at(i).portName;
            tempfriendname = ports.at(i).friendName;
        } else {}
    }
    QString portName = tempportname;              // update this to use your port of choice
    if (portName == "NULL"){ qDebug() << "SerialDevice NOT FOUND portName = " << portName;
    }else{ qDebug() << " SerialDevice FOUND portName = " << portName; }
    return portName;
}
 
PortListener::PortListener(const QString & portName) {  //, int iVal){     //portName = this->enumerate();
    if (portName=="NULL"){ //NOT CONNECTED
    }else{ SetPort(portName);  }
}
 
void PortListener::SetPort(const QString & portName){   
    this->port = new QextSerialPort(portName, QextSerialPort::EventDriven);
    port->setBaudRate(BAUD115200);
    port->setFlowControl(FLOW_OFF);
    port->setParity(PAR_NONE);
    port->setDataBits(DATA_8);
    port->setStopBits(STOP_1);          
    if (port->open(QIODevice::ReadWrite) == true) {
        connect(port, SIGNAL(readyRead()), this, SLOT(onReadyRead()));
        connect(port, SIGNAL(dsrChanged(bool)), this, SLOT(onDsrChanged(bool)));
        if (!(port->lineStatus() & LS_DSR))
            qDebug() << "warning: device is not turned on";
        qDebug() << "listening for data on" << port->portName();
    }
    else {qDebug() << "device failed to open:" << port->errorString(); }
    emit onReadyWrite("Listener Created!");
}