7.4 Qt 开发 网络编程

Qt网络编程采用事件驱动模型，通过信号槽机制实现异步通信，避免了传统阻塞式网络编程的复杂性。

一、基于 TCP 的网络编程

TCP是面向连接的、可靠的、基于流的传输协议。在Qt中，服务器端使用QTcpServer监听连接，客户端使用QTcpSocket连接服务器。

• 服务器端实现：

// 创建TCP服务器
QTcpServer *tcpServer = new QTcpServer(this);

// 监听指定地址和端口
if (!tcpServer->listen(QHostAddress::Any, 12345)) {
    qDebug() << "Server could not start:" << tcpServer->errorString();
} else {
    qDebug() << "Server started on port 12345";
}

// 新连接到达时的处理
connect(tcpServer, &QTcpServer::newConnection, this, [=]() {
    // 获取与客户端通信的套接字
    QTcpSocket *clientSocket = tcpServer->nextPendingConnection();
    
    // 记录客户端信息
    qDebug() << "New connection from:" << clientSocket->peerAddress().toString() 
             << ":" << clientSocket->peerPort();
    
    // 接收数据
    connect(clientSocket, &QTcpSocket::readyRead, this, [=]() {
        // TCP是流式协议，可能需要处理粘包/拆包
        QByteArray data = clientSocket->readAll();
        qDebug() << "Received from client:" << data;
        
        // 示例：回显数据
        clientSocket->write("Server echo: " + data);
    });
    
    // 处理连接断开
    connect(clientSocket, &QTcpSocket::disconnected, this, [=]() {
        qDebug() << "Client disconnected";
        clientSocket->deleteLater();  // 安全删除套接字
    });
    
    // 处理错误
    connect(clientSocket, &QTcpSocket::errorOccurred, this, [=](QAbstractSocket::SocketError error) {
        qDebug() << "Socket error:" << clientSocket->errorString();
    });
});

• 客户端实现：

// 创建TCP套接字
QTcpSocket *tcpSocket = new QTcpSocket(this);

// 连接状态变化的处理
connect(tcpSocket, &QTcpSocket::connected, this, [=]() {
    qDebug() << "Connected to server";
    
    // 发送数据
    QString message = "Hello, Server!";
    tcpSocket->write(message.toUtf8());
    qDebug() << "Sent:" << message;
});

connect(tcpSocket, &QTcpSocket::disconnected, this, [=]() {
    qDebug() << "Disconnected from server";
});

// 异步连接到服务器
tcpSocket->connectToHost("127.0.0.1", 12345);

// 接收数据
connect(tcpSocket, &QTcpSocket::readyRead, this, [=]() {
    QByteArray data = tcpSocket->readAll();
    qDebug() << "Received from server:" << data;
});

// 错误处理
connect(tcpSocket, &QTcpSocket::errorOccurred, this, [=](QAbstractSocket::SocketError error) {
    qDebug() << "Connection error:" << tcpSocket->erro