c++ - 诡异的 QTcpSocket 行为

问题描述

在调试接下来的几行代码时，我一直在做噩梦，一定有一些东西隐藏在我所看到的之外。

这是客户端和服务器之间的连接

QByteArray Client::request(QByteArray cmd)
{
    //DEBUG << "Command: " << cmd.toStdString().c_str();
    QTcpSocket *socket = new QTcpSocket(this);
    socket->connectToHost(hostAddress, port, QIODevice::ReadWrite);
    if (socket->waitForConnected(TIMEOUT))
    {
        socket->write(cmd);
        DEBUG << "Size of bytes written :" << sizeof (cmd);
    }
    else DEBUG << "Couldn't connect to socket";
    if (socket->waitForBytesWritten(TIMEOUT)) DEBUG << "Command sent";
    else DEBUG << "Couldn't write to socket";
    if (socket->waitForReadyRead(TIMEOUT))
    {
        QByteArray data = socket->readAll();
        socket->close();
        return data;
    }
    else DEBUG << "No reply from Server";
    return QByteArray();
}

对于客户端和服务器来说，基本上就是这样，这里是重要的片段。

class ConnectionHandler : public QTcpServer
{
    Q_OBJECT


public:
    explicit ConnectionHandler(QObject *parent = 0);
    void write(QByteArray);

protected:
    void ConnectionHandler::incomingConnection(qintptr descriptor)
{
    DEBUG << "ConnectionHandler:" << "Incoming Connection :" << descriptor;
    ConnectionThread *thread = new ConnectionThread(this, descriptor);
    connect(thread, &QThread::finished, thread, &QThread::deleteLater);
    connect(thread, &ConnectionThread::signalIncomingMessage, this, &ConnectionHandler::slotIncomingMessage);
    connect(this, &ConnectionHandler::signalOutgoingMessage, thread, &ConnectionThread::slotOutgoingMessage);
    thread->start();
}

public slots:
    void slotIncomingMessage(QByteArray);
    void slotListen(bool checked){
    if (checked)
    {
        if (!this->listen(QHostAddress::LocalHost, PORT_NUMBER)) {
            DEBUG << "ConnectionHandler:" << "Could not start the server!";
        } else {
            DEBUG << "ConnectionHandler:" << "Listening...";
        }
    } else {
        this->close();
        DEBUG << "ConnectionHandler:" << "Connection Closed!";
    }
}

signals:
    void signalOutgoingMessage(QByteArray);
};

class ConnectionThread : public QThread
{
    Q_OBJECT
public:
    ConnectionThread(QObject* parent = 0, qintptr descriptor = -1){
    if (descriptor != -1)
    {
        socket = new QTcpSocket();

        DEBUG << "ConnectionThread: Connecting to socket number" << descriptor;
        if (!socket->setSocketDescriptor(descriptor))
        {
            DEBUG << "ConnectionThread: Connection failed.";
            DEBUG << socket->errorString();
        }
        else
        {
            DEBUG << "ConnectionThread: Connected Successfully.";
            connect(socket, &QAbstractSocket::disconnected, this, &ConnectionThread::slotSocketDisconnected);
        }
    }
    else {
        DEBUG << "ConnectionThread: Please provide a descriptor for the connection thread";
    }
}
    void run() override{
    if (socket->state() != QAbstractSocket::ConnectedState)
    {
        DEBUG << "ConnectionThread: Socket is not connected!";
        DEBUG << "ConnectionThread: Closing Thread!";
        emit signalThreadError(socket->errorString());
    }
    else
    {
        DEBUG << "ConnectionThread: Socket is Connected.";
        connect(socket, &QIODevice::readyRead, this, &ConnectionThread::slotThreadReadyRead, Qt::DirectConnection);
        exec();
    }
}

signals:
    void signalThreadError(QString);
    void signalIncomingMessage(QByteArray);

public slots:
    void slotThreadReadyRead(){
    QByteArray msg = socket->readAll();

    if (!msg.isEmpty()) {
        emit signalIncomingMessage(msg);
    }

    DEBUG << "ConnectionThread: Data in:" << msg;
}
    void slotSocketDisconnected();
    void slotOutgoingMessage(QByteArray msg)
{
    if (socket != nullptr) {
        socket->write(msg);
        if (socket->waitForBytesWritten(TIMEOUT)) {
            DEBUG << "ConnectionThread: Outgoing Message: " << msg;
        } else {
            DEBUG << "ConnectionThread: Outgoing Message Timeout";
        }
    }
}

private:
    QTcpSocket *socket = nullptr;
};

基本上会发生什么，它有时会收到来自客户端的传入命令，而大多数时候它不会，不仅如此，它实际上会接收一些命令并忽略一些不同的命令。

这是一个更诡异的行为，注意中的行//DEBUG << "Command: " << cmd.toStdString().c_str();，Client::request()当这行被注释掉时，服务器实际上收到了一些命令，如果没有，服务器是聋的。

这是该行被注释掉时的输出：

Size of bytes written : 8
Command sent
target num = 4  (a reply was received)
Size of bytes written : 8
Command sent
No reply from Server

当提到的行没有被注释掉时，这是另一个输出：

Command:  NUMB

Size of bytes written : 8
Command sent
No reply from Server
target num = 0
Command:  TRAN

Size of bytes written : 8
Command sent
No reply from Server

更新解决在客户端写入套接字和线程打开之间发生的竞争对我来说是这样做的，在我的情况下线程使用是不必要的，所以我只是放弃了它。由@Botje 回答

标签： c++qtqtcpsocketqtcpserver

c++ - 诡异的 QTcpSocket 行为

问题描述

解决方案

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