Frustrating problem with QextSerialPort write()

[calhal]

while (inpSt.compare("quit") != 0)
    {
        std::getline(std::cin, inpSt);
        std::cerr << serialPort->write(inpSt.c_str());
        std::cerr << "Sent command: " << inpSt << std::endl;
    }

while (inpSt.compare("quit") != 0)
    {
        std::getline(std::cin, inpSt);
        std::cerr << serialPort->write(inpSt.c_str());
        std::cerr << "Sent command: " << inpSt << std::endl;
    }

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What do you get from this on stderr?
And am I missing something or you're not opening the port in your code?
The rest as wysota wrote