QProcess 和 QLocalSocket - 未收到 IPC 消息

Question

有一个 QLocalServer 的子类，它使用 Qprocess 启动另一个应用程序（客户端），该客户端将使用 QLocalSocket 发送一些消息。只有当客户端进程退出时，只有来自客户端的第一条消息才会出现在主（服务器）应用程序中。

服务器应用程序：

localserver.h

#ifndef LOCALSERVER_H
#define LOCALSERVER_H

#include <QLocalServer>

class LocalServer : public QLocalServer
{
    Q_OBJECT

public:

    explicit LocalServer(QObject* prnt = nullptr);
};

#endif // LOCALSERVER_H

localserver.cpp

#include "localserver.h"

#include <QLocalSocket>
#include <QDebug>

LocalServer::LocalServer(QObject* prnt)
    : QLocalServer(prnt)
{
    connect(this, &QLocalServer::newConnection, this, [&]() {
        qDebug() << "Socket connected";
        QLocalSocket* socket = this->nextPendingConnection();
        connect(socket, &QLocalSocket::disconnected, socket, &QLocalSocket::deleteLater);
        connect(socket, &QLocalSocket::readyRead, [&, socket]() {
            qDebug() << socket->readAll();
        });
    });
}

main.cpp（服务器）

#include <QCoreApplication>
#include <QProcess>

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

    LocalServer::removeServer("testServer");
    LocalServer server;

    if (server.listen("testServer")) {
        QProcess process;
        process.setProgram("/home/ram/work/build/QtExamples/build-LocalSocketClient-Qt_5_12_1_Desktop-Debug/LocalSocketClient");
        process.start();

        if (process.waitForStarted() && process.waitForFinished()) {
            a.exit(0);
        }
    }

    return a.exec();
}

客户端应用程序：

main.cpp（客户端）

#include <QCoreApplication>

#include <QLocalSocket>
#include <QTimer>
#include <QDebug>

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

    QLocalSocket localSocket;

    QObject::connect(&localSocket, &QLocalSocket::connected, &localSocket, []() {
        qDebug() << "Socket connected";
    });

    localSocket.setServerName("testServer");
    localSocket.connectToServer();

    if (localSocket.waitForConnected()) {
        qDebug() << "Connected!";
        auto timer = new QTimer(qApp);
        QObject::connect(timer, &QTimer::timeout, &localSocket, [&localSocket]() {
            static int msgCount(0);
            QString msg(QString("Message from client %1").arg(++msgCount));
            qDebug() << localSocket.write(msg.toLatin1()) << msg;

            if (msgCount > 5) {
                qApp->exit(0);
            }
        });
        timer->start(1000);
    } else {
        return 1;
    }

    return a.exec();
}

当我运行两个应用程序分开时，即在服务器应用程序的 main.cpp 中没有 Qprocess 部分，我看到以下输出。

Socket connected
"Message from client 1"
"Message from client 2"
"Message from client 3"
"Message from client 4"
"Message from client 5"

在 QProcess 中，所有五个消息同时出现。

Socket connected
"Message from client 1Message from client 2Message from client 3Message from client 4Message from client 5"

我在这里遗漏了什么吗？ QProcess 需要更多信息吗？

此外，我也尝试使用 system() 函数 - 它的行为相同。

Answer 1

切勿使用 waitXXX 方法，因为它们会阻塞事件循环以阻止信号传输。在您的情况下，数据是一个接一个地获取的，但是因为没有人消耗信息，因为信号没有传输，所以它会累积在缓冲区中，并且仅在事件循环未被阻止时显示所有文本。因此，您的解决方案不是使用 waitXXX 而是使用信号：

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

    LocalServer::removeServer("testServer");
    LocalServer server;

    if (server.listen("testServer")) {
        QProcess process;
        process.setProgram("/home/ram/work/build/QtExamples/build-LocalSocketClient-Qt_5_12_1_Desktop-Debug/LocalSocketClient");
        process.start();
        QObject::connect(&process, QOverload<int>::of(&QProcess::finished), &QCoreApplication::quit);
        return a.exec();
    }
    return 0;
}

QProcess 和 QLocalSocket - 未收到 IPC 消息

QProcess and QLocalSocket - IPC messages aren't received

c++

qt

qprocess

qt5