C++/Qt - 从一个线程到另一个线程槽的信号

Question

我正在设置一个使用QTcpSocket 的客户端。设置与服务器连接的部分是作为线程实现的。

这是我的类的样子，它实现了连接函数 (.hpp):

class Connector: public QObject {
Q_OBJECT
public:
Connector(QString hexHost);
virtual ~Connector();

// Start to establish a connection
void startConnection();
// End thread
void stopConnection();

signals:
// Emitted, if connector should get to work
void startTransforming();
// Emitted, if transformation from hex to dig is complete
void transformationFinished();
// Emitted, if connection is established
void connectionEstd();
// Emitted, if connection failed
void connectionFailed();
// Emitted, if work is done
void doneConnecting();

public slots:
// Connect to server
void connectToServer();

private:
// IP of the server
QString addressHost;
// Socket
QTcpSocket aQTcpSocket;
};

这就是我实现此类 (.cpp) 的方式；

Connector::Connector(QString hexHost)
{
// Save user data
addressHost = hexHost;

// Start thread
bool result = QObject::connect(this, SIGNAL(startTransforming()), this, SLOT(transformIP()));
Q_ASSERT(result);

// Start trying to establish a connection
result = QObject::connect(this, SIGNAL(transformationFinished()), this, SLOT(connectToServer()));
Q_ASSERT(result);

// End thread
result = QObject::connect(this, SIGNAL(doneConnecting()), this, SLOT(deleteLater()));
Q_ASSERT(result);
Q_UNUSED(result);
}

Connector::~Connector()
{
QObject::disconnect(this, SIGNAL(startTransforming()), this, SLOT(transformIP()));
QObject::disconnect(this, SIGNAL(transformationFinished()), this, SLOT(connectToServer()));
QObject::disconnect(this, SIGNAL(doneConnecting()), this, SLOT(deleteLater()));
}

void Connector::transformIP()
{
[...]

// Emit ready signal
emit transformationFinished();
}

void Connector::connectToServer()
{
aQTcpSocket.connectToHost(addressHost, port);
    result = aQTcpSocket.waitForConnected(5000);

    if(result)
{
    emit connectionFailed();
    emit doneConnecting();
        std::clog << "Connection failed!" << std::endl;   // This debug message is printed during runtime
    return;
    }

// Emit signal
emit connectionEstd();
}

void Connector::startConnection()
{
emit startTransforming();
}

void Connector::stopConnection()
{
emit doneConnecting();
}

我通过以下方式开始线程:

[...]

// Create new thread
QThread *conThread = new QThread();
// Create connector object
aConnector = new Connector(hexHost);
aConnector->moveToThread(conThread);
conThread->start();

// Clean up thread
bool result = QObject::connect(aConnector, SIGNAL(destroyed()), conThread, SLOT(quit()));
Q_ASSERT(result);

result = QObject::connect(conThread, SIGNAL(finished()), conThread, SLOT(deleteLater()));
Q_ASSERT(result);

// Connect signals
result = QObject::connect(aConnector, SIGNAL(connectionFailed()), this, SLOT(onConnectionFailed()));
Q_ASSERT(result);

result = QObject::connect(aConnector, SIGNAL(connectionEstd()), this, SLOT(onConnectionEstd()));
Q_ASSERT(result);
Q_UNUSED(result);

// Get connector to work
aConnector->startConnection();

[...]

当我测试程序时，连接器创建正确。他启动函数 transformIP() 和 connectToServer()。目前我没有运行服务器，因此客户端无法连接。这应该导致发出信号 连接失败()使用连接器对象启动线程的客户端类应接收此信号并对其作出 react 。

问题是:信号似乎没有发出，因为客户端类没有对它使用react。这是客户端类中的部分，我将信号连接到某个插槽:

 // Connect signals
result = QObject::connect(aConnector, SIGNAL(connectionFailed()), this, SLOT(onConnectionFailed()));
Q_ASSERT(result);

如果有人知道如何解决这个问题，那就太好了，谢谢 :)

Answer 1

看起来QTcpSocket.connectToHost返回值是空的，调用是异步的。您需要做的是调用 QTcpSocket.connectToHost() 并使用 QTcpSocket.waitForConnected( CONNECT_TIME_OUT ) 等待连接完成，然后处理错误的连接

例子:

QTcpSocket socket;
socket.connectToHost(QHostAddress("172.0.0.1", 8080);
if (!socket.waitForConnected(5000)) {
    emit connectionFailed();
}