QProcess 和 QLocalSocket - 未收到 IPC 消息

Question

遵循财富客户端示例。

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，也只有在客户端进程退出时才会出现。

服务器应用：

本地服务器.h

#ifndef LOCALSERVER_H
#define LOCALSERVER_H
#include <QLocalServer>
class LocalServer : public QLocalServer
{
    Q_OBJECT
public:
    explicit LocalServer(QObject* prnt = nullptr);
};
#endif // LOCALSERVER_H

本地服务器.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();
        });
    });
}

主.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：

主.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();
}

当我分别运行两个应用程序时，即没有Qprocess服务器应用程序中main.cpp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"

有了QProcess所有五条消息都会同时出现。

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

我在这里错过了什么吗？QProcess还需要信息吗？

另外，我也尝试使用system()函数 - 它的行为相同。

Answer 1

切勿使用 waitXXX 方法，因为它们会阻塞信号传输的事件循环。在您的情况下，数据是逐个获取的，但由于信号未传输，因此没有人使用信息，因此它会积聚在缓冲区中，并且仅在事件循环未被阻塞时才显示显示所有文本。因此，在您的情况下，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;
}