QSerialPort::readyRead() is not emitted, but QTCPSocket::readyRead() works fine.

[Rufledore]

@jsulm said in QSerialPort::readyRead() is not emitted, but QTCPSocket::readyRead() works fine.:

As I mentioned in the first post it is a part of a shared library that I develop. So, this library has export functions like these:

MLXCOM_API int MLXCOM_CALL_CONV mlxcom_send_data(MLXCOM_CHANNEL mlxcomChannel, char* data, uint32_t dataSize) {
    MLXCOMChannel* channel = static_cast<MLXCOMChannel*>(mlxcomChannel);
    QByteArray dataForSend(data, dataSize);

    channel->prepareErrorHandler();
    channel->sendData(dataForSend);
    if (channel->hasNewError()) {
        return channel->lastError().first;
    }

    return 0;
}

// add parameter - number of bytes.
MLXCOM_API int MLXCOM_CALL_CONV mlxcom_receive_data(MLXCOM_CHANNEL mlxcomChannel, char* data, uint32_t data_size) {
    MLXCOMChannel* channel = static_cast<MLXCOMChannel*>(mlxcomChannel);

    channel->prepareErrorHandler();
    QByteArray msg = channel->receiveData(data_size);
    if (msg.size() > 0) {
        std::memcpy(data, msg.data(), static_cast<size_t>(msg.size() + 1));
    }
    if (channel->hasNewError()) {
        return channel->lastError().first;
    }


    return 0;
}

So I added a function init() where I did QCoreApplication::exec().

I use the library in a test console application that is only a main(), but doesn't have QApplication or QCoreApplication in it. There I faced the issue. When I use the library in a test UI app that is simply a MainWindow started from main() and QApplication.exec() it works okay. However I am willing do make cross platform C-style library that could be used not only in Qt. TCP communication class works well also when I use it in visual studio.

[Rufledore]

Okay, now I tried it and the static way QCoreApplication::exec() doesn't block but throw : QApplication::exec: Please instantiate the QApplication object first

[Rufledore]

I didn't mentioned also that it something actually turns the event loop sometimes and the signal is emitted, but not regularly. I think that it is waitForBytesWritten(). If I don't use waitForBytesWritten while writing to device nothing happens.

[Christian Ehrlicher]

@Rufledore said in QSerialPort::readyRead() is not emitted, but QTCPSocket::readyRead() works fine.:

QApplication::exec: Please instantiate the QApplication object first

Then you should do this in our main() in the first line.

[Rufledore]

@Christian-Ehrlicher said in QSerialPort::readyRead() is not emitted, but QTCPSocket::readyRead() works fine.:

@Rufledore said in QSerialPort::readyRead() is not emitted, but QTCPSocket::readyRead() works fine.:

QApplication::exec: Please instantiate the QApplication object first

Then you should do this in our main() in the first line.

In principle yes, but I don't want the user of the library to bother with Qt staff as QApplication. And the main question for me is how it works okay for TCPSocket but not for SerialPort?

[Christian Ehrlicher]

You need a working QCoreApplication - everything else simply works by accident and may not work suddenly.

[Rufledore]

Then how to use Qt specific features as signals and slots in a library? QCoreApplication could be started only in main thread... If I start it on the background it doesn't work well. Could you give me an idea, how to proceed?

[kuzulis]

@Rufledore said in QSerialPort::readyRead() is not emitted, but QTCPSocket::readyRead() works fine.:

Could you give me an idea, how to proceed?

Quick answer - nohow, it makes not sense to use Qt stuff from the non-qt libraries.

[Christian Ehrlicher]

@Rufledore said in QSerialPort::readyRead() is not emitted, but QTCPSocket::readyRead() works fine.:

could be started only in main thread

Q(Core|Gui)Application can also be started in another thread but then all gui operations must be done inside this thread too.

[Rufledore]

@Rufledore said in QSerialPort::readyRead() is not emitted, but QTCPSocket::readyRead() works fine.:

Then how to use Qt specific features as signals and slots in a library? QCoreApplication could be started only in main thread... If I start it on the background it doesn't work well. Could you give me an idea, how to proceed?

It is a Qt library but not for Qt application :)

[JonB]

@Rufledore
I don't think you can use Qt library calls for TCP/serial port without being in a Qt application. As in, they don't work properly, as you have discovered. They need parts of the Q(Core|Gui)Application-type architecture.,