c++ - 从另一个线程(子线程)访问QTcpSocket

Question

我创建了一个包含QTcpServer 的线程，它接受任何传入的连接:

void Service::run() //Service class is a subclass of QThread
{
    server->listen(QHostAddress::LocalHost, ServicePortNo);
    // server is a private member of Service    

    while(server->waitForNewConnection(-1)){
        QTcpSocket *socket = server->nextPendingConnection();
        handle(socket); // This is a pure virtual function
    }
}

在 handle(QTcpSocket *socket) 中:

// TimeDateService is subclass of Service
// implementation of pure virtual function handle()
void TimeDateService::handle(QTcpSocket *socket)
{
    (new TimeDateSocketHandler(socket))->Start();
}

注意:TimeDateSocketHandler是SocketHandler的子类，SocketHandler本身是QThread的子类如下图:

void SocketHandler::run()
{
    if(!socket->waitForReadyRead(WAIT_TIMEOUT))
    {
        socket->disconnectFromHost();
        socket->close();
        return;
    }
    QByteArray request = socket->readAll();
    QByteArray response = Serve(request); // Serve is a pure virtual function
    socket->write(response);
    socket->waitForBytesWritten(WAIT_TIMEOUT);
    socket->disconnectFromHost();
    socket->close();
}

最后是 TimeDateSocketHandler

QByteArray TimeDateSocketHandler::Serve(QByteArray request)
{
    QByteArray response;
    response.append(QTime::currentTime().toString().toUtf8());
    response.append(QString(SEPARATOR).toUtf8());
    response.append(QDate::currentDate().toString().toUtf8());
    return response;
}

主要功能:

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

    TimeDateService timedateService;
    //CalculatorService calculatorService;
    //RemoteCMDService remoteCMDService;

    timedateService.StartService();
    //calculatorService.StartService();
    //remoteCMDService.StartService();

    return a.exec();
}

在 main 函数中，我启动了 TimeDateService。但是，当我连接到服务器以检索时间和日期时，服务器会发送时间和日期，但是当 TimeDateSocketHandler 想要关闭套接字时，程序崩溃了:

ASSERT failure in QCoreApplication::sendEvent: "Cannot send events to objects ow ned by a different thread. Current thread 3998779bf0. Receiver '' (of type 'QNat iveSocketEngine') was created in thread 39985efcd0", file kernel\qcoreapplicatio n.cpp, line 494

谁能帮我解决这个问题，非常感谢

Answer 1

你的问题是这一行:

(new TimeDateSocketHandler(socket))->Start();

父“套接字”位于 TimeDateService 线程中，但子“套接字”位于 TimeDateocketHandler 线程中。使用 Qt 事件循环时父子应该在同一个线程中。

这里是 documentation 的相关部分:

Event filters are supported in all threads, with the restriction that the monitoring object must live in the same thread as the monitored object. Similarly, QCoreApplication::sendEvent() (unlike postEvent()) can only be used to dispatch events to objects living in the thread from which the function is called. Here is an example of that:

解决方案相对简单:

• 您可以直接使用 invokeMethod method of QMetaObject 调用该方法.您需要使用排队连接来在单独的线程中触发插槽。

  QMetaObject::invokeMethod(new TimeDateSocketHandler(socket), 插槽(开始())， Qt::QueuedConnection);

或

• 使用信号和槽。这意味着发出一个信号而不是直接调用，然后连接另一个线程的相应插槽。

  TimeDateSocketHandler *timeDateSocketHandler = new TimeDateSocketHandler(socket);

  connect(this, SIGNAL(socketHandled()), timeDateSocketHandler, SLOT(Start()));

  发出 socketHandled();

或

• 使用智能指针(如 QSharedPointer)代替原始指针

• 将套接字处理移至另一个线程。