<![CDATA[[Solved] QSerialPort close() throws Unknown error]]>Hi,
Im talking with my GSM-Modem with QSerialPort.
At the beginning i do the following:
@QSerialPort* pSerialPort = new QSerialPort(this);@

I have a "start()" Funktion within i do this:

@pSerialPort->setPortName(sPortName);

if (pSerialPort->open(QIODevice::ReadWrite))
{
    if (pSerialPort->setBaudRate(QSerialPort::Baud19200)
            && pSerialPort->setDataBits(QSerialPort::Data8)
            && pSerialPort->setParity(QSerialPort::NoParity)
            && pSerialPort->setStopBits(QSerialPort::OneStop)
            && pSerialPort->setFlowControl(QSerialPort::NoFlowControl))
    {
        connect(pSerialPort, SIGNAL(error(QSerialPort::SerialPortError)), this, SLOT(serialPortError(QSerialPort::SerialPortError)));
        connect(pSerialPort, SIGNAL(readyRead()), this, SLOT(serialRead()));
        stateMaschine(START);
        emit info("GsmCommunication::start(): COM-Schnittstelle erfolgreich initialisiert", GlobalVars::SI_COM_PORT_INIT_OK);
        pSmsCheckTimer->start();

    }
    else
    {
        emit error("GsmCommunication::start(): Kann COM-Schnittstelle nicht initialisieren");
    }
}
else
{
    emit error("GsmCommunication::start(): Kann COM-Schnittstelle nicht oeffnen");
}@

I have a "stop()"-function within i do this:

@pSerialPort->clear();
pSerialPort->close();@

And i have a reInit()-function, within i do this:

@stop();
start();@

Everything works fine, but i get "Unknown error" from QSerialPort when i call my reInit()-Function. Seems like QSerialPort.close() causes the error, why is that?

]]>https://forum.qt.io/topic/35163/solved-qserialport-close-throws-unknown-errorRSS for NodeThu, 24 Sep 2026 15:20:56 GMTFri, 06 Dec 2013 09:58:03 GMT60<![CDATA[Reply to [Solved] QSerialPort close() throws Unknown error on Tue, 10 Dec 2013 09:48:52 GMT]]>bq. *ERROR: 0 ErrorString: “Unknown error”

This is not an error. Just ignore/skip SerialPortError::NoError error code.. :)

]]>https://forum.qt.io/post/206890https://forum.qt.io/post/206890Tue, 10 Dec 2013 09:48:52 GMT<![CDATA[Reply to [Solved] QSerialPort close() throws Unknown error on Tue, 10 Dec 2013 09:25:06 GMT]]>I changed my Modification in the terminal example:

@void MainWindow::handleError(QSerialPort::SerialPortError error)
{
qDebug() << "ERROR: " << error << "ErrorString: " << serial->errorString();
if (error == QSerialPort::ResourceError) {
QMessageBox::critical(this, tr("Critical Error"), serial->errorString());
closeSerialPort();
}
}@
Now the terminal example shows the following in debugging console:
*ERROR: 0 ErrorString: "Unknown error" *
Thats exactly the same behaivior as in my Program.

The USB->RS232 converter is type U232-P9 made in Taiwan (-: dont have more information.

I will have to read about the Git Version and how to compile it, never heard about that so far.

]]>https://forum.qt.io/post/206886https://forum.qt.io/post/206886Tue, 10 Dec 2013 09:25:06 GMT<![CDATA[Reply to [Solved] QSerialPort close() throws Unknown error on Tue, 10 Dec 2013 08:46:07 GMT]]>bq. Since then also the terminal-example shows “ERROR: 0”

It is NoError.

bq. “pSerialPort->clear()” just before “open()” is called, since then i get the following Error-String

It is because your port already closed, so the clear() method can't to be success.

bq. USB->RS232 connector

What is connector model?

bq. I use the build in Version of QSerialPort in QT 5.1.1

Please download and compile the Git version of QtSerialPort and try check again.

Also:

  1. Please provide a minimal compilable project that reproduce a problem (it is better - console if possible).

  2. You can try to do debugging himself to help us.

]]>https://forum.qt.io/post/206882https://forum.qt.io/post/206882Tue, 10 Dec 2013 08:46:07 GMT<![CDATA[Reply to [Solved] QSerialPort close() throws Unknown error on Tue, 10 Dec 2013 07:40:05 GMT]]>Ty for ur answer,
I tried it with the terminal example, i added the following code to see any kind of errors:

@void MainWindow::handleError(QSerialPort::SerialPortError error)
{
qDebug() << "ERROR: " << error; //I added this line
if (error == QSerialPort::ResourceError) {
QMessageBox::critical(this, tr("Critical Error"), serial->errorString());
closeSerialPort();
}
}@
Since then also the terminal-example shows "ERROR: 0", but not as I thought when close() is called, it appears when I click the "connect" button, also in my Program it appears in my start() function. I added "pSerialPort->clear()" just before "open()" is called, since then i get the following Error-String:
"Das Handle ist ungültig." Which i would translate in english as "The Handle is not valid". Without the clear() its "Unknown Error".

The OS is Microsoft Windows 7 32bit.
The Device is a CT63 GSM-Modem conneted with a USB->RS232 connector.
I use the build in Version of QSerialPort in QT 5.1.1
(#include <QtSerialPort/QSerialPort>)
I fixed the issue of wrong placed connect(), but that doesnt appear to make any changes.

]]>https://forum.qt.io/post/206872https://forum.qt.io/post/206872Tue, 10 Dec 2013 07:40:05 GMT<![CDATA[Reply to [Solved] QSerialPort close() throws Unknown error on Fri, 06 Dec 2013 10:45:25 GMT]]>

  • Can you try it with the Terminal example (from the QtSerialPort package)?
    I mean just do clicks to the "connect" and "disconnect" buttons.

  • What OS is used?

  • What model of modem is used (what is device)?

  • What version of QSerialPort you use? From the Git?

  • The QObject::connect should be done once after creation of the QSerialPort's object, like:

    • @
    QSerialPort* pSerialPort = new QSerialPort(this);

    connect(pSerialPort, SIGNAL(error(QSerialPort::SerialPortError)),
    this, SLOT(serialPortError(QSerialPort::SerialPortError)));

    connect(pSerialPort, SIGNAL(readyRead()), this, SLOT(serialRead()));
    @

    ]]>    https://forum.qt.io/post/206537https://forum.qt.io/post/206537Fri, 06 Dec 2013 10:45:25 GMT