使用 Linux 伪终端测试 QSerialPort

Question

我想使用带有伪终端的 Qt 串行端口测试应用程序。根据我实施的手册页：

// open master
QSerialPort master("/dev/ptmx");
master.open(QSerialPort::ReadWrite);
int master_fd = master.handle();

// get device name of slave pseudoterminal
constexpr size_t PTSNAME_BUFFER_LENGTH = 128;
char ptsname_buffer[PTSNAME_BUFFER_LENGTH];
if (ptsname_r(master_fd, ptsname_buffer, PTSNAME_BUFFER_LENGTH) != 0)
    return 0;

// grant access to the slave
if (grantpt(master_fd) != 0)
    return 0;

// unlock the slave
if (unlockpt(master_fd) != 0)
    return 0;

// open slave
std::cout << "Slave pseudoterminal: " << ptsname_buffer << std::endl;
QSerialPort slave(ptsname_buffer);
slave.open(QSerialPort::ReadWrite);

// test communication
master.write("Hello World");
std::this_thread::sleep_for(std::chrono::milliseconds(500));
std::cout << "Received: " << slave.readAll().toStdString() << std::endl;

创建从属设备似乎可行（在我的例子中，它是在 /dev/pts/2 处创建的）。但是，slave.readAll() 命令总是 returns 一个空字符串。

是否可以使用伪终端测试 QSerialPort？

Answer 1

Qt 在事件循环中执行，因此您需要等待通信被处理，在 Qt 中您应该使用信号异步工作：

main.cpp

#include <QCoreApplication>
#include <QSerialPort>

#include <iostream>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QSerialPort master("/dev/ptmx");
    if(!master.open(QSerialPort::ReadWrite))
        std::cout<<"The master port was not opened";

    int master_fd = master.handle();

    // get device name of slave pseudoterminal
    constexpr size_t PTSNAME_BUFFER_LENGTH = 128;
    char ptsname_buffer[PTSNAME_BUFFER_LENGTH];
    if (ptsname_r(master_fd, ptsname_buffer, PTSNAME_BUFFER_LENGTH) != 0)
        return -1;

    // grant access to the slave
    if (grantpt(master_fd) != 0)
        return -1;

    // unlock the slave
    if (unlockpt(master_fd) != 0)
        return -1;

    // open slave
    std::cout << "Slave pseudoterminal: " << ptsname_buffer << std::endl;
    QSerialPort slave(ptsname_buffer);
    if(!slave.open(QSerialPort::ReadWrite))
        std::cout<<"The slave port was not opened";

    QObject::connect(&slave, &QSerialPort::readyRead, [&](){
        std::cout << "Received: " << slave.readAll().toStdString() << std::endl;
        a.quit();
    });
    // test communication
    master.write("Hello World");
    return a.exec();
}

输出：

Slave pseudoterminal: /dev/pts/3
Received: Hello World

注意：不要使用std::this_thread::sleep_for，因为它是阻止事件循环执行的阻塞任务。

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