网络编程

Qt 提供了强大的网络编程支持，包括 HTTP 请求、TCP/UDP 通信等功能。

QNetworkAccessManager（HTTP 请求）

用于发送 HTTP 请求和处理响应。

GET 请求

#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QNetworkRequest>

class HttpClient : public QObject
{
    Q_OBJECT
    
public:
    HttpClient(QObject *parent = nullptr) : QObject(parent)
    {
        manager = new QNetworkAccessManager(this);
    }
    
    void get(const QString &url)
    {
        QNetworkRequest request(QUrl(url));
        request.setHeader(QNetworkRequest::ContentTypeHeader, "application/json");
        
        QNetworkReply *reply = manager->get(request);
        
        connect(reply, &QNetworkReply::finished, this, [=]() {
            if (reply->error() == QNetworkReply::NoError) {
                QByteArray data = reply->readAll();
                QString text = QString::fromUtf8(data);
                qDebug() << "响应:" << text;
            } else {
                qDebug() << "错误:" << reply->errorString();
            }
            reply->deleteLater();
        });
    }
    
private:
    QNetworkAccessManager *manager;
};

POST 请求

void post(const QString &url, const QJsonObject &json)
{
    QNetworkRequest request(QUrl(url));
    request.setHeader(QNetworkRequest::ContentTypeHeader, "application/json");
    
    QJsonDocument doc(json);
    QByteArray data = doc.toJson();
    
    QNetworkReply *reply = manager->post(request, data);
    
    connect(reply, &QNetworkReply::finished, this, [=]() {
        if (reply->error() == QNetworkReply::NoError) {
            QByteArray response = reply->readAll();
            QJsonDocument doc = QJsonDocument::fromJson(response);
            QJsonObject obj = doc.object();
            // 处理响应
        }
        reply->deleteLater();
    });
}

// 使用示例
QJsonObject json;
json["username"] = "admin";
json["password"] = "123456";
post("https://api.example.com/login", json);

文件下载

void downloadFile(const QString &url, const QString &savePath)
{
    QNetworkRequest request(QUrl(url));
    QNetworkReply *reply = manager->get(request);
    
    QFile *file = new QFile(savePath);
    if (!file->open(QIODevice::WriteOnly)) {
        delete file;
        return;
    }
    
    connect(reply, &QNetworkReply::readyRead, this, [=]() {
        file->write(reply->readAll());
    });
    
    connect(reply, &QNetworkReply::finished, this, [=]() {
        file->close();
        delete file;
        reply->deleteLater();
        
        if (reply->error() == QNetworkReply::NoError) {
            qDebug() << "下载完成";
        }
    });
    
    // 下载进度
    connect(reply, &QNetworkReply::downloadProgress, this, 
        [=](qint64 bytesReceived, qint64 bytesTotal) {
        if (bytesTotal > 0) {
            int percent = static_cast<int>((bytesReceived * 100) / bytesTotal);
            qDebug() << "下载进度:" << percent << "%";
        }
    });
}

QTcpSocket（TCP 客户端）

#include <QTcpSocket>

class TcpClient : public QObject
{
    Q_OBJECT
    
public:
    TcpClient(QObject *parent = nullptr) : QObject(parent)
    {
        socket = new QTcpSocket(this);
        
        connect(socket, &QTcpSocket::connected, this, [=]() {
            qDebug() << "已连接到服务器";
        });
        
        connect(socket, &QTcpSocket::disconnected, this, [=]() {
            qDebug() << "与服务器断开连接";
        });
        
        connect(socket, &QTcpSocket::readyRead, this, [=]() {
            QByteArray data = socket->readAll();
            qDebug() << "收到数据:" << data;
        });
        
        connect(socket, QOverload<QAbstractSocket::SocketError>::of(&QTcpSocket::error),
            this, [=](QAbstractSocket::SocketError error) {
            qDebug() << "错误:" << socket->errorString();
        });
    }
    
    void connectToHost(const QString &host, quint16 port)
    {
        socket->connectToHost(host, port);
    }
    
    void send(const QByteArray &data)
    {
        if (socket->state() == QAbstractSocket::ConnectedState) {
            socket->write(data);
        }
    }
    
    void disconnect()
    {
        socket->disconnectFromHost();
    }
    
private:
    QTcpSocket *socket;
};

QTcpServer（TCP 服务器）

#include <QTcpServer>
#include <QTcpSocket>

class TcpServer : public QObject
{
    Q_OBJECT
    
public:
    TcpServer(QObject *parent = nullptr) : QObject(parent)
    {
        server = new QTcpServer(this);
        
        connect(server, &QTcpServer::newConnection, this, [=]() {
            QTcpSocket *client = server->nextPendingConnection();
            clients.append(client);
            
            qDebug() << "新客户端连接:" << client->peerAddress().toString();
            
            connect(client, &QTcpSocket::readyRead, this, [=]() {
                QByteArray data = client->readAll();
                qDebug() << "收到:" << data;
                // 广播给所有客户端
                broadcast(data, client);
            });
            
            connect(client, &QTcpSocket::disconnected, this, [=]() {
                qDebug() << "客户端断开";
                clients.removeAll(client);
                client->deleteLater();
            });
        });
    }
    
    bool start(quint16 port)
    {
        return server->listen(QHostAddress::Any, port);
    }
    
    void broadcast(const QByteArray &data, QTcpSocket *except = nullptr)
    {
        for (QTcpSocket *client : clients) {
            if (client != except && client->state() == QAbstractSocket::ConnectedState) {
                client->write(data);
            }
        }
    }
    
private:
    QTcpServer *server;
    QList<QTcpSocket*> clients;
};

QUdpSocket（UDP 通信）

#include <QUdpSocket>

class UdpClient : public QObject
{
    Q_OBJECT
    
public:
    UdpClient(QObject *parent = nullptr) : QObject(parent)
    {
        socket = new QUdpSocket(this);
        socket->bind(QHostAddress::Any, 12345);
        
        connect(socket, &QUdpSocket::readyRead, this, [=]() {
            while (socket->hasPendingDatagrams()) {
                QByteArray datagram;
                datagram.resize(socket->pendingDatagramSize());
                QHostAddress sender;
                quint16 port;
                
                socket->readDatagram(datagram.data(), datagram.size(), &sender, &port);
                qDebug() << "收到来自" << sender.toString() << ":" << port << "的数据:" << datagram;
            }
        });
    }
    
    void send(const QByteArray &data, const QString &host, quint16 port)
    {
        socket->writeDatagram(data, QHostAddress(host), port);
    }
    
private:
    QUdpSocket *socket;
};

下一步

Qt 网络编程基础已介绍完毕。建议继续深入学习 Qt 的线程编程，以实现高效的网络通信应用。