Qt网络开发以及QTcpSocket::waitForBytesWritten()的问题

开发一个包含较重的网络传输(发送)负载的程序时,在一个QThread辅助线程中使用QTcpSocket::waitForBytesWritten()等待发送操作完成。发现时常诱发QAbstractSocket::SocketTimeoutError,甚至出现难以调试的崩溃问题。

一种处理措施:将QTcpSocket::waitForBytesWritten()调用替换为QTcpSocket::flush()调用。或仅执行QTcpSocket::write()写操作,由Qt事件循环处理所有工作。使用此方法时,可能需要跨线程共享QTcpSocket对象,此时对QTcpSocket对象的定义和引用应全部通过指针在堆区完成,并进行加锁保护(有助于在一定程度上避免高速调用时的栈错误)。

另一种处理措施:使用一个继承自QObject工作者子对象将对QTcpSocket的初始化和引用全部置于QThread辅助线程中进行。使用一个同时包含了工作者子对象和QThread辅助线程的、继承自QObject的控制类进行管理。子类被控制类通过moveToThread()函数整体移入QThread线程内并做好信号与槽之间的连接,启动线程后,即可使用子线程自己的事件循环进行调度和管理。

同时,由于Qt的TCP/UDP套接字本身即为异步执行,因此在主线程工作负载相对较轻、网络速度较快、不使用发送队列的场合,没有必要使用多线程机制。

/* HEADER FILE */
 
#include <QApplication>
#include <QHostAddress>
#include <QMap>
#include <QMutex>
#include <QMutexLocker>
#include <QQueue>
#include <QReadWriteLock>
#include <QString>
#include <QTcpSocket>
#include <QThread>
#include <QTimer>
#include <QVector>
 
/* TCP Networking Data Sending Thread Worker Object */
//This object is moved to a child thread to have its own event loop
class TCPClientDataSender : public QTcpSocket {
    Q_OBJECT
 
public:
    explicit TCPClientDataSender();
    ~TCPClientDataSender();
 
    /* Data Sending Status Indicator */
    bool IsDataSending() const;
 
public slots:
    /* Connection Management Command Handlers */
    void ConnectToServerRequestedEventHandler(const QString sServerIPNew, quint16 iPortNew,
                                              bool bIsAutoReconnectEnabledNew, unsigned int iAutoReconnectDelayNew, bool bWairForOperationToComplete);
    void DisconnectFromServerRequestedEventHandler(bool bWairForOperationToComplete);
    void SetAutoReconnectOptionsRequestedEventHandler(bool bIsAutoReconnectEnabledNew, unsigned int iAutoReconnectDelayNew);
    void SendDataToServerRequestedEventHandler();
 
signals:
    void SocketConnectedToServerEvent(QString sServerName, QString sServerIPAddress, quint16 iServerPort);
    void SocketDisconnectedFromServerEvent(QString sServerName, QString sServerIPAddress, quint16 iServerPort);
    void SocketErrorOccurredEvent(QAbstractSocket::SocketError errErrorInfo, QString sServerName, QString sServerIPAddress, quint16 iServerPort);
    void SocketResponseReceivedFromServerEvent(QString sResponse, QString sServerName, QString sServerIPAddress, quint16 iServerPort);
 
private:
    QString sServerIP; //INTERNAL: Remote IP Address
    quint16 iPort; //INTERNAL: Remote port
    bool bIsAutoReconnectEnabled; //INTERNAL: Is auto reconnect function on
    unsigned int iAutoReconnectDelay; //INTERNAL: Auto reconnect retry interval
    bool bIsUserInitiatedDisconnection; //INTERNAL: Marks if user has initiated a disconnection, to avoid unexpected TryReconnect() flooding
    bool bIsReconnecting; //INTERNAL: Marks if we are alreading waiting a reconnection, to avoid unexpected TryReconnect() flooding
    volatile bool bIsDataSending; //INTERNAL: Marks if we are sending data, avoid recursive calling of SendDataToServerRequestedEventHandler() and segmentation faults
 
private slots:
    /* TCP Socket Event Handler Slots */
    void TCPClientDataSender_Connected();
    void TCPClientDataSender_Disconnected();
    void TCPClientDataSender_Error(QAbstractSocket::SocketError errErrorInfo);
    void TCPClientDataSender_ReadyRead();
 
    /* Functional Slots */
    void TryReconnect();
};
 
/* TCP Networking Client Wrapper */
class TCPClient : public QObject {
    Q_OBJECT
 
public:
    TCPClient(); //Default constructor, loads options from ini file or default values
    TCPClient(const QString sServerIPNew, quint16 iPortNew,
              bool bIsAutoReconnectEnabledNew, unsigned int iAutoReconnectDelayNew); //Constructor with options. Will update options saved in ini file
    ~TCPClient();
 
    /* Options Management */
    void LoadSettings(); //Load settings
    void SaveSettings() const; //Save settings
 
    /* TCP Socket Object Management */
    bool IsConnected() const; //Get if we have connected to a remote server
 
    /* Connection Management */
    void SetServerParameters(const QString sServerIPNew, quint16 iPortNew); //Host information (IP & Port)
    const QString & GetServerIP() const;
    quint16 GetServerPort() const;
    void ConnectToServer(bool bWairForOperationToComplete = false); //Connect to remote server with saved values
    void ConnectToServer(const QString sServerIPNew, quint16 iPortNew,
                         bool bIsAutoReconnectEnabledNew = false, unsigned int iAutoReconnectDelayNew = 0, bool bWairForOperationToComplete = false); //Connect to remote server with given address and port. Will update options saved in ini file
    void DisconnectFromServer(bool bWairForOperationToComplete = false); //Disconnect
    void SendDataToServer();
 
    /* Options */
    void SetAutoReconnectMode(bool bIsAutoReconnectEnabledNew); //Set & Get auto reconnect function (handles error events)
    bool GetIsAutoReconnectEnabled() const;
    void SetAutoReconnectDelay(unsigned int iAutoReconnectDelayNew); //Set & Get auto reconnect retry interval
    unsigned int GetAutoReconnectDelay() const;
 
    /* Validators */
    bool IsValidIPAddress(const QString sIPAddress) const; //Check if the given address is valid
    bool IsValidTCPPort(quint16 iPort, bool bUseRegisteredPortsOnly = true) const; //Check if the given port ID is valid (typically in the range of [1,65535], or [1024,32767] if bUseRegisteredPortsOnly is true)
 
public slots:
    /* Worker Object Event Handler */
    void SocketResponseReceivedFromServerEventHandler(QString sResponse, QString sServerName, QString sServerIPAddress, quint16 iServerPort);
 
signals:
    /* Signals to Communicate with Worker Object */
    void ConnectToServerRequestedEvent(const QString sServerIPNew, quint16 iPortNew,
                                       bool bIsAutoReconnectEnabledNew, unsigned int iAutoReconnectDelayNew, bool bWairForOperationToComplete);
    void DisconnectFromServerRequestedEvent(bool bWairForOperationToComplete);
    void SetAutoReconnectOptionsRequestedEvent(bool bIsAutoReconnectEnabledNew, unsigned int iAutoReconnectDelayNew);
    void SendDataToServerRequestedEvent();
 
    /* Signals to Communicate with Upper Layer */
    void ResponseReceivedFromServerEvent(QString sResponse, QString sServerName, QString sServerIPAddress, quint16 iServerPort);
    void ConnectedToServerEvent(QString sServerName, QString sServerIPAddress, quint16 iServerPort);
    void DisconnectedFromServerEvent(QString sServerName, QString sServerIPAddress, quint16 iServerPort);
    void NetworkingErrorOccurredEvent(QAbstractSocket::SocketError errErrorInfo, QString sServerName, QString sServerIPAddress, quint16 iServerPort);
 
private:
    /* Threads & Worker Objects */
    QThread * trdTCPDataSender; //Thread which is used to host and control worker thread
    TCPClientDataSender * tcpDataSender; //Worker object
 
    /* Options Var */
    QString sServerIP; //INTERNAL: Remote IP Address
    quint16 iPort; //INTERNAL: Remote port
    bool bIsAutoReconnectEnabled; //INTERNAL: Is auto reconnect function on
    unsigned int iAutoReconnectDelay; //INTERNAL: Auto reconnect retry interval
};
 
/* TCP Client */
extern TCPClient * tcpDataClient;
 
/* IMPLEMENTATION */
 
/* TCP Client */
TCPClient * tcpDataClient;
 
/* TCP Networking Data Sending Thread Worker Object */
TCPClientDataSender::TCPClientDataSender() {
    //Initialize internal variables
    bIsDataSending = false;
    bIsUserInitiatedDisconnection = false;
    bIsReconnecting = false;
 
    //Create TCP socket object and connect events
    connect(this, SIGNAL(connected()), this, SLOT(TCPClientDataSender_Connected()));
    connect(this, SIGNAL(disconnected()), this, SLOT(TCPClientDataSender_Disconnected()));
    qRegisterMetaType<QAbstractSocket::SocketError>("QAbstractSocket::SocketError"); //Register QAbstractSocket::SocketError type for QueuedConnection
    connect(this, SIGNAL(error(QAbstractSocket::SocketError)), this, SLOT(TCPClientDataSender_Error(QAbstractSocket::SocketError)));
    connect(this, SIGNAL(readyRead()), this, SLOT(TCPClientDataSender_ReadyRead()));
}
 
TCPClientDataSender::~TCPClientDataSender() {
}
 
/* Data Sending Status Indicator */
bool TCPClientDataSender::IsDataSending() const {
    return bIsDataSending;
}
 
/* Connection Management Command Handlers */
void TCPClientDataSender::ConnectToServerRequestedEventHandler(const QString sServerIPNew, quint16 iPortNew,
                                                               bool bIsAutoReconnectEnabledNew, unsigned int iAutoReconnectDelayNew, bool bWairForOperationToComplete) {
    sServerIP = sServerIPNew;
    iPort = iPortNew;
    bIsAutoReconnectEnabled = bIsAutoReconnectEnabledNew;
    iAutoReconnectDelay = iAutoReconnectDelayNew;
    bIsUserInitiatedDisconnection = false;
 
    connectToHost(sServerIPNew, iPortNew);
    if (bWairForOperationToComplete) {
        waitForConnected();
    }
 
    return;
}
 
void TCPClientDataSender::DisconnectFromServerRequestedEventHandler(bool bWairForOperationToComplete) {
    disconnectFromHost();
    bIsUserInitiatedDisconnection = true;
    bIsReconnecting = false;
    if (bWairForOperationToComplete) {
        waitForDisconnected();
    }
    return;
}
 
void TCPClientDataSender::SetAutoReconnectOptionsRequestedEventHandler(bool bIsAutoReconnectEnabledNew, unsigned int iAutoReconnectDelayNew) {
    bIsAutoReconnectEnabled = bIsAutoReconnectEnabledNew;
    iAutoReconnectDelay = iAutoReconnectDelayNew;
    return;
}
 
void TCPClientDataSender::SendDataToServerRequestedEventHandler() {
    //Check if SendDataToServerRequestedEventHandler() is running, avoid recursive calling of SendDataToServerRequestedEventHandler() and segmentation faults
    if (bIsDataSending) {
        //If this is a recursive calling, simply returns
        return;
    }
    else {
        //Marks SendDataToServerRequestedEventHandler() is running
        bIsDataSending = true;
    }
 
    //Send data to remote
    //You can maintain a data queue to cache data panding sending
 
    bIsDataSending = false;
    return;
}
 
/* TCP Socket Event Handler Slots */
void TCPClientDataSender::TCPClientDataSender_Connected() {
    qDebug() << "TCPClient: Connected to" << sServerIP << ":" << iPort;
    bIsReconnecting = false;
    emit SocketConnectedToServerEvent(peerName(), sServerIP, iPort);
    return;
}
 
void TCPClientDataSender::TCPClientDataSender_Disconnected() {
    qDebug() << "TCPClient: Disconnected from" << sServerIP << ":" << iPort;
    emit SocketDisconnectedFromServerEvent(peerName(), sServerIP, iPort);
    return;
}
 
void TCPClientDataSender::TCPClientDataSender_Error(QAbstractSocket::SocketError errErrorInfo) {
    qDebug() << "TCPClient: Error" << errErrorInfo << ": " << errorString();
    if (state() != QTcpSocket::UnconnectedState) {
        disconnectFromHost();
        waitForDisconnected(245000);
    }
    if (bIsAutoReconnectEnabled && !bIsReconnecting && !bIsUserInitiatedDisconnection) { //Check if we need to reconnect
        qDebug() << "TCPClient: Will retry connect after" << iAutoReconnectDelay << "ms";
        QTimer::singleShot(iAutoReconnectDelay, this, SLOT(TryReconnect()));
        bIsReconnecting = true;
    }
    emit SocketErrorOccurredEvent(errErrorInfo, peerName(), sServerIP, iPort);
    return;
}
 
void TCPClientDataSender::TCPClientDataSender_ReadyRead() {
    while (bytesAvailable()) {
        //Read a command line and emit a signal
        emit SocketResponseReceivedFromServerEvent(readLine(), peerName(), sServerIP, iPort);
 
        //Process events
        //QApplication::processEvents();
    }
    return;
}
 
/* Functional Slots */
void TCPClientDataSender::TryReconnect() {
    if (bIsUserInitiatedDisconnection) {
        return;
    }
    if (state() != QTcpSocket::ConnectingState && state() != QTcpSocket::ConnectedState) {
        qDebug() << "TCPClient: Retrying to connect to" << sServerIP << ":" << iPort;
        connectToHost(sServerIP, iPort);
        waitForConnected(245000);
    }
    if (state() != QTcpSocket::ConnectedState) {
        qDebug() << "TCPClient: Will retry connect after" << iAutoReconnectDelay << "ms";
        if (state() != QTcpSocket::UnconnectedState) {
            disconnectFromHost();
            waitForDisconnected(245000);
        }
        QTimer::singleShot(iAutoReconnectDelay, this, SLOT(TryReconnect()));
    }
    return;
}
 
/* TCP Networking Client Wrapper */
TCPClient::TCPClient() {
    //Load settings
    TCPClient::LoadSettings();
 
    //Create worker object
    tcpDataSender = new TCPClientDataSender;
 
    //Creat thread object and move worker object (and all it's child objects) to this thread
    trdTCPDataSender = new QThread;
    tcpDataSender->moveToThread(trdTCPDataSender);
 
    //Connect events and handlers
    connect(this, SIGNAL(ConnectToServerRequestedEvent(QString, quint16, bool, unsigned int, bool)), tcpDataSender, SLOT(ConnectToServerRequestedEventHandler(QString, quint16, bool, unsigned int, bool)));
    connect(this, SIGNAL(DisconnectFromServerRequestedEvent(bool)), tcpDataSender, SLOT(DisconnectFromServerRequestedEventHandler(bool)));
    connect(this, SIGNAL(SetAutoReconnectOptionsRequestedEvent(bool, uint)), tcpDataSender, SLOT(SetAutoReconnectOptionsRequestedEventHandler(bool, uint)));
    connect(this, SIGNAL(SendDataToServerRequestedEvent()), tcpDataSender, SLOT(SendDataToServerRequestedEventHandler()));
    connect(tcpDataSender, SIGNAL(SocketResponseReceivedFromServerEvent(QString, QString, QString, quint16)), this, SLOT(SocketResponseReceivedFromServerEventHandler(QString, QString, QString, quint16)));
    connect(tcpDataSender, SIGNAL(SocketConnectedToServerEvent(QString, QString, quint16)), this, SIGNAL(ConnectedToServerEvent(QString, QString, quint16)));
    connect(tcpDataSender, SIGNAL(SocketDisconnectedFromServerEvent(QString, QString, quint16)), this, SIGNAL(DisconnectedFromServerEvent(QString, QString, quint16)));
    connect(tcpDataSender, SIGNAL(SocketErrorOccurredEvent(QAbstractSocket::SocketError, QString, QString, quint16)), this, SIGNAL(NetworkingErrorOccurredEvent(QAbstractSocket::SocketError, QString, QString, quint16)));
 
    //Start child thread's own event loop
    trdTCPDataSender->start();
}
 
TCPClient::TCPClient(const QString sServerIPNew, quint16 iPortNew,
                     bool bIsAutoReconnectEnabledNew, unsigned int iAutoReconnectDelayNew) {
    //Save settings
    sServerIP = sServerIPNew;
    iPort = iPortNew;
    bIsAutoReconnectEnabled = bIsAutoReconnectEnabledNew;
    iAutoReconnectDelay = iAutoReconnectDelayNew;
    TCPClient::SaveSettings();
 
    //Create worker object
    tcpDataSender = new TCPClientDataSender;
 
    //Creat thread object
    trdTCPDataSender = new QThread;
    tcpDataSender->moveToThread(trdTCPDataSender);
 
    //Connect events and handlers
    connect(this, SIGNAL(ConnectToServerRequestedEvent(QString, quint16, bool, unsigned int, bool)), tcpDataSender, SLOT(ConnectToServerRequestedEventHandler(QString, quint16, bool, unsigned int, bool)));
    connect(this, SIGNAL(DisconnectFromServerRequestedEvent(bool)), tcpDataSender, SLOT(DisconnectFromServerRequestedEventHandler(bool)));
    connect(this, SIGNAL(SetAutoReconnectOptionsRequestedEvent(bool, uint)), tcpDataSender, SLOT(SetAutoReconnectOptionsRequestedEventHandler(bool, uint)));
    connect(this, SIGNAL(SendDataToServerRequestedEvent()), tcpDataSender, SLOT(SendDataToServerRequestedEventHandler()));
    connect(tcpDataSender, SIGNAL(SocketResponseReceivedFromServerEvent(QString, QString, QString, quint16)), this, SLOT(SocketResponseReceivedFromServerEventHandler(QString, QString, QString, quint16)));
    connect(tcpDataSender, SIGNAL(SocketConnectedToServerEvent(QString, QString, quint16)), this, SIGNAL(ConnectedToServerEvent(QString, QString, quint16)));
    connect(tcpDataSender, SIGNAL(SocketDisconnectedFromServerEvent(QString, QString, quint16)), this, SIGNAL(DisconnectedFromServerEvent(QString, QString, quint16)));
    connect(tcpDataSender, SIGNAL(SocketErrorOccurredEvent(QAbstractSocket::SocketError, QString, QString, quint16)), this, SIGNAL(NetworkingErrorOccurredEvent(QAbstractSocket::SocketError, QString, QString, quint16)));
 
    //Start child thread's own event loop
    trdTCPDataSender->start();
}
 
TCPClient::~TCPClient() {
    //Save settings
    if (TCPClient::IsConnected()) {
        TCPClient::DisconnectFromServer();
    }
    TCPClient::SaveSettings();
 
    //Quit child thread
    trdTCPDataSender->quit();
    if (!trdTCPDataSender->wait(1000)) {
        trdTCPDataSender->terminate();
    }
 
    //Delete worker object
    tcpDataSender->deleteLater();
    tcpDataSender = NULL;
 
    //Delete child thread
    trdTCPDataSender->deleteLater();
    trdTCPDataSender = NULL;
}
 
/* Options Management */
void TCPClient::LoadSettings() {
    //Load settings from persistent storage or something else
    return;
}
 
void TCPClient::SaveSettings() const {
    //Save settings to persistent storage or something else
    return;
}
 
/* TCP Socket Object Management */
bool TCPClient::IsConnected() const {
    return (tcpDataSender->state() == QTcpSocket::ConnectedState);
}
 
/* Connection Management */
void TCPClient::SetServerParameters(const QString sServerIPNew, quint16 iPortNew) {
    if (TCPClient::IsValidIPAddress(sServerIPNew) && TCPClient::IsValidTCPPort(iPortNew)) {
        //Save settings
        sServerIP = sServerIPNew;
        iPort = iPortNew;
        TCPClient::SaveSettings();
    }
    return;
}
 
const QString & TCPClient::GetServerIP() const {
    return sServerIP;
}
 
quint16 TCPClient::GetServerPort() const {
    return iPort;
}
 
void TCPClient::ConnectToServer(bool bWairForOperationToComplete) {
    emit ConnectToServerRequestedEvent(sServerIP, iPort, bIsAutoReconnectEnabled, iAutoReconnectDelay, bWairForOperationToComplete);
    return;
}
 
void TCPClient::ConnectToServer(const QString sServerIPNew, quint16 iPortNew,
                                bool bIsAutoReconnectEnabledNew, unsigned int iAutoReconnectDelayNew, bool bWairForOperationToComplete) {
    //Save settings
    sServerIP = sServerIPNew;
    iPort = iPortNew;
    bIsAutoReconnectEnabled = bIsAutoReconnectEnabledNew;
    iAutoReconnectDelay = iAutoReconnectDelayNew;
    TCPClient::SaveSettings();
 
    //Connect
    emit ConnectToServerRequestedEvent(sServerIP, iPort, bIsAutoReconnectEnabled, iAutoReconnectDelay, bWairForOperationToComplete);
    return;
}
 
void TCPClient::DisconnectFromServer(bool bWairForOperationToComplete) {
    emit DisconnectFromServerRequestedEvent(bWairForOperationToComplete);
    return;
}
 
void TCPClient::SendDataToServer() {
    //In high frame rate mode, avoid SendDataToServerRequestedEvent() signal flooding
    if (tcpDataSender->IsDataSending()) {
        return;
    }
    emit SendDataToServerRequestedEvent();
    return;
}
 
/* Options */
void TCPClient::SetAutoReconnectMode(bool bIsAutoReconnectEnabledNew) {
    bIsAutoReconnectEnabled = bIsAutoReconnectEnabledNew;
    TCPClient::SaveSettings();
    emit SetAutoReconnectOptionsRequestedEvent(bIsAutoReconnectEnabled, iAutoReconnectDelay);
    return;
}
 
bool TCPClient::GetIsAutoReconnectEnabled() const {
    return bIsAutoReconnectEnabled;
}
 
void TCPClient::SetAutoReconnectDelay(unsigned int iAutoReconnectDelayNew) {
    iAutoReconnectDelay = iAutoReconnectDelayNew;
    TCPClient::SaveSettings();
    emit SetAutoReconnectOptionsRequestedEvent(bIsAutoReconnectEnabled, iAutoReconnectDelay);
    return;
}
 
unsigned int TCPClient::GetAutoReconnectDelay() const {
    return iAutoReconnectDelay;
}
 
/* Worker Object Event Handler */
void TCPClient::SocketResponseReceivedFromServerEventHandler(QString sResponse, QString sServerName, QString sServerIPAddress, quint16 iServerPort) {
    qDebug() << "TCPClient: Response" << sResponse << "received from the remote";
    emit ResponseReceivedFromServerEvent(sResponse, sServerName, sServerIPAddress, iServerPort);
    return;
}
 
/* Validators */
bool TCPClient::IsValidIPAddress(const QString sIPAddress) const {
    QHostAddress hstTestAddr;
    return hstTestAddr.setAddress(sIPAddress);
}
 
bool TCPClient::IsValidTCPPort(quint16 iPort, bool bUseRegisteredPortsOnly) const {
    quint16 iPortIDMin = 1, iPortIDMax = 65535;
    if (bUseRegisteredPortsOnly) {
        iPortIDMin = 1024;
        iPortIDMax = 32767;
    }
    return ((iPort >= iPortIDMin) && (iPort <= iPortIDMax));
}
it
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