QT socket waitfor函数

waitfor函数是QT中QIODevice类的一个成员函数，用于等待读取到指定的数据，或者达到指定的超时时间。

该函数的定义如下：

bool QIODevice::waitForReadyRead(int msecs = 30000)

其中，msecs参数表示等待的最长时间，单位是毫秒，默认值为30000毫秒，即30秒。

该函数的返回值为bool类型，如果读取到指定数据或者达到指定超时时间，返回true，否则返回false。

举例来说，如果我们想要从一个QT的socket中读取数据，可以使用如下代码：

QTcpSocket *socket = new QTcpSocket(this);
socket->connectToHost("127.0.0.1", 1234);
if (socket->waitForReadyRead()) {
    QByteArray data = socket->readAll();
    qDebug() << data;
}

这段代码中，我们先创建了一个QTcpSocket对象，然后连接到了本地IP地址为127.0.0.1，端口号为1234的服务器。接着，我们调用了waitForReadyRead函数等待读取数据，如果读取到了数据，我们就可以使用readAll函数读取所有数据并打印出来。

相关问题

QT TCP 文件上传下载

### 使用 QT 和 TCP 实现文件上传和下载

为了实现基于QT的TCP文件传输功能，可以扩展基本的TCP服务器和客户端模型，在此基础上加入文件读写操作。下面展示了一个简化版的例子，该例子包含了启动服务器、连接到服务器以及发送/接收文件的主要逻辑。

#### 创建TCP服务器端用于接受文件

服务器部分负责监听来自客户端的连接请求并准备接收数据流中的文件内容：

#include <QCoreApplication>
#include <QTcpServer>
#include <QTcpSocket>
#include <QFile>

class FileTransferServer : public QObject {
    Q_OBJECT
public:
    explicit FileTransferServer(QObject *parent = nullptr);

private slots:
    void onNewConnection();
    void startReceiving();

private:
    QTcpServer* server;
};

void FileTransferServer::onNewConnection() {
    QTcpSocket* clientConnection = server->nextPendingConnection();
    connect(clientConnection, &QTcpSocket::readyRead, this, &FileTransferServer::startReceiving);
}

void FileTransferServer::startReceiving() {
    QTcpSocket* socket = qobject_cast<QTcpSocket*>(sender());
    QFile file("received_file");
    if (!file.open(QIODevice::WriteOnly)) {
        qDebug() << "Cannot open file for writing";
        return;
    }
    
    QByteArray data = socket->readAll();
    file.write(data);
    file.close();
}

此段代码实现了当有新的客户端尝试建立连接时触发`onNewConnection()`函数，并设置好回调以便于接收到数据后调用`startReceiving()`处理实际的数据保存工作[^1]。

#### 构建TCP客户端以发送文件

对于客户端而言，则需先与指定地址上的服务端建立起有效的套接字链接，之后再将本地选定的目标文件逐块传递给对方：

#include <QCoreApplication>
#include <QTcpSocket>
#include <QFile>

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

    QTcpSocket tcpSocket;
    QString hostAddress = "127.0.0.1"; // Replace with your server IP address.
    quint16 portNumber = 8080;         // Use the same port number as defined by the server.

    tcpSocket.connectToHost(hostAddress, portNumber);

    if (tcpSocket.waitForConnected(5000)) { // Wait up to five seconds before timing out.
        QFile localFile("path_to_your_file");

        if (!localFile.open(QIODevice::ReadOnly)){
            qDebug()<<"Failed to open file.";
            return -1;
        }

        while(!localFile.atEnd()){
            QByteArray block = localFile.read(64*1024); // Read chunks of max size 64KB at once.
            tcpSocket.write(block);
            tcpSocket.flush();                          // Ensure all bytes are sent immediately.
        }

        localFile.close();
        tcpSocket.disconnectFromHost();
        
        qDebug()<<"File transfer completed successfully!";
    } else{
        qDebug()<<"Error: Could not establish connection.";
    }

    return a.exec();
}

上述C++片段展示了怎样利用QTcpSocket类完成向远程主机传送特定路径下存储的文档的任务；这里假设目标机器上运行着兼容的服务进程等待接收这些信息包[^2]。

qt wifi mesh 中节点自组网代码

以下是一个基于 Qt 的 WiFi Mesh 自组网示例代码：

#include <QCoreApplication>
#include <QNetworkConfigurationManager>
#include <QNetworkSession>
#include <QProcess>
#include <QTimer>
#include <QSocketNotifier>
#include <QDebug>

// WiFi Mesh 自组网示例代码

#define CONFIG_FILE "/etc/wpa_supplicant.conf"
#define CONFIG_TEMPLATE "ctrl_interface=/var/run/wpa_supplicant\n\
update_config=1\n\
\n\
network={\n\
    ssid=\"%1\"\n\
    mode=1\n\
    frequency=2412\n\
    proto=RSN\n\
    key_mgmt=WPA-PSK\n\
    pairwise=CCMP\n\
    group=CCMP\n\
    psk=\"%2\"\n\
}"

class Node : public QObject
{
    Q_OBJECT
public:
    Node(const QString& name, const QString& ssid, const QString& password);

public slots:
    void start();
    void stop();

private slots:
    void readStdout();
    void readStderr();
    void processError(QProcess::ProcessError error);
    void processFinished(int exitCode, QProcess::ExitStatus exitStatus);
    void networkSessionOpened();
    void networkSessionClosed();
    void socketActivated(int fd);

private:
    QString m_name;
    QString m_ssid;
    QString m_password;
    QString m_configFilePath;
    QProcess m_process;
    QNetworkConfigurationManager m_networkConfigManager;
    QNetworkSession* m_networkSession;
    QTimer m_timer;
    QSocketNotifier* m_socketNotifier;
};

Node::Node(const QString& name, const QString& ssid, const QString& password)
    : QObject(nullptr)
    , m_name(name)
    , m_ssid(ssid)
    , m_password(password)
    , m_configFilePath(QString("/etc/wpa_supplicant-%1.conf").arg(name))
    , m_process(this)
    , m_networkConfigManager(this)
    , m_networkSession(nullptr)
    , m_timer(this)
    , m_socketNotifier(nullptr)
{
    connect(&m_process, &QProcess::readyReadStandardOutput, this, &Node::readStdout);
    connect(&m_process, &QProcess::readyReadStandardError, this, &Node::readStderr);
    connect(&m_process, static_cast<void(QProcess::*)(int, QProcess::ExitStatus)>(&QProcess::finished), this, &Node::processFinished);
    connect(&m_process, &QProcess::errorOccurred, this, &Node::processError);
    connect(&m_networkConfigManager, &QNetworkConfigurationManager::onlineStateChanged, this, &Node::networkSessionClosed);
    connect(&m_timer, &QTimer::timeout, this, &Node::start);
}

void Node::start()
{
    if (m_networkSession && m_networkSession->isOpen()) {
        qDebug() << "Node" << m_name << "is already connected to the network";
        return;
    }

    qDebug() << "Starting node" << m_name << "...";

    // Write the configuration file for this node
    QFile configFile(m_configFilePath);
    if (configFile.open(QIODevice::WriteOnly | QIODevice::Text)) {
        QTextStream out(&configFile);
        out << QString(CONFIG_TEMPLATE).arg(m_ssid).arg(m_password);
        configFile.close();
    } else {
        qCritical() << "Error writing configuration file for node" << m_name;
        return;
    }

    // Start the wpa_supplicant process
    QStringList arguments;
    arguments << "-Dnl80211" << "-c" << m_configFilePath;
    m_process.start("wpa_supplicant", arguments);

    // Wait for the process to start and create the control socket
    if (m_process.waitForStarted()) {
        m_socketNotifier = new QSocketNotifier(m_process.handle(), QSocketNotifier::Read, this);
        connect(m_socketNotifier, &QSocketNotifier::activated, this, &Node::socketActivated);
    } else {
        qCritical() << "Error starting wpa_supplicant for node" << m_name;
    }

    // Wait for the network session to be opened
    if (!m_networkSession) {
        m_networkSession = new QNetworkSession(m_networkConfigManager.defaultConfiguration(), this);
        connect(m_networkSession, &QNetworkSession::opened, this, &Node::networkSessionOpened);
        connect(m_networkSession, &QNetworkSession::closed, this, &Node::networkSessionClosed);
    } else {
        networkSessionOpened();
    }
}

void Node::stop()
{
    qDebug() << "Stopping node" << m_name << "...";

    // Stop the wpa_supplicant process
    m_process.terminate();
    if (!m_process.waitForFinished(5000)) {
        m_process.kill();
    }

    // Delete the configuration file for this node
    QFile::remove(m_configFilePath);

    // Close the network session
    if (m_networkSession) {
        m_networkSession->close();
    }
}

void Node::readStdout()
{
    qDebug() << "Node" << m_name << "stdout:" << m_process.readAllStandardOutput();
}

void Node::readStderr()
{
    qWarning() << "Node" << m_name << "stderr:" << m_process.readAllStandardError();
}

void Node::processError(QProcess::ProcessError error)
{
    qCritical() << "Node" << m_name << "process error:" << error << m_process.errorString();
}

void Node::processFinished(int exitCode, QProcess::ExitStatus exitStatus)
{
    qDebug() << "Node" << m_name << "process finished with exit code" << exitCode << "and exit status" << exitStatus;
}

void Node::networkSessionOpened()
{
    qDebug() << "Node" << m_name << "network session opened:" << m_networkSession->isOpen();
}

void Node::networkSessionClosed()
{
    qDebug() << "Node" << m_name << "network session closed:" << !m_networkSession->isOpen();
    m_networkSession = nullptr;
    m_socketNotifier = nullptr;
    m_timer.start(1000);
}

void Node::socketActivated(int fd)
{
    char buffer[1024];
    int length = read(fd, buffer, sizeof(buffer));
    if (length > 0) {
        qDebug() << "Node" << m_name << "control socket message:" << QString::fromUtf8(buffer, length);
    }
}

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

    // Start the nodes
    Node node1("node1", "mesh", "password");
    Node node2("node2", "mesh", "password");
    Node node3("node3", "mesh", "password");
    node1.start();
    node2.start();
    node3.start();

    // Stop the nodes after 10 seconds
    QTimer::singleShot(10000, &node1, &Node::stop);
    QTimer::singleShot(10000, &node2, &Node::stop);
    QTimer::singleShot(10000, &node3, &Node::stop);

    return a.exec();
}

#include "main.moc"

在上面的示例代码中，我们定义了一个 Node 类，它代表一个 WiFi Mesh 网络中的节点。在 Node 类的构造函数中，我们传入了节点的名称、SSID 和密码，同时生成了一个节点专用的 wpa_supplicant 配置文件。在 Node 类的 start() 方法中，我们启动了 wpa_supplicant 进程，并且等待它创建控制套接字。我们还创建了一个 QNetworkSession 对象，用于连接到 WiFi 网络，等待连接成功后，我们就可以使用这个节点了。在 Node 类的 stop() 方法中，我们停止了 wpa_supplicant 进程，并且删除了节点专用的 wpa_supplicant 配置文件。