qt tcp proxy

Qt中可以使用QTcpServer和QTcpSocket实现TCP代理，具体步骤如下：

1. 创建一个QTcpServer实例并监听指定端口。

2. 当有客户端连接时，创建一个QTcpSocket实例并连接到目标服务器。

3. 将QTcpServer的newConnection()信号与槽函数连接，当有新的客户端连接时，获取客户端的QTcpSocket实例，并将其与目标服务器的QTcpSocket实例进行数据传输。

4. 在数据传输的过程中，需要分别处理客户端和目标服务器的QTcpSocket实例的readyRead()信号，以及对应的槽函数。

5. 在数据传输结束后，需要关闭和释放所有的QTcpServer和QTcpSocket实例。

下面是一个简单的TCP代理的示例代码：

#include <QTcpServer>
#include <QTcpSocket>

class TcpProxy : public QTcpServer {
    Q_OBJECT
public:
    TcpProxy(QObject *parent = nullptr) : QTcpServer(parent) {}

protected:
    void incomingConnection(qintptr socketDescriptor) override {
        QTcpSocket *clientSocket = new QTcpSocket(this);
        clientSocket->setSocketDescriptor(socketDescriptor);

        QTcpSocket *serverSocket = new QTcpSocket(this);
        serverSocket->connectToHost("target_host", target_port);

        connect(clientSocket, SIGNAL(readyRead()), this, SLOT(onClientReadyRead()));
        connect(serverSocket, SIGNAL(readyRead()), this, SLOT(onServerReadyRead()));
        connect(clientSocket, SIGNAL(disconnected()), this, SLOT(onClientDisconnected()));
        connect(serverSocket, SIGNAL(disconnected()), this, SLOT(onServerDisconnected()));

        m_clientSockets.insert(clientSocket, serverSocket);
        m_serverSockets.insert(serverSocket, clientSocket);
    }

private slots:
    void onClientReadyRead() {
        QTcpSocket *clientSocket = qobject_cast<QTcpSocket *>(sender());
        QTcpSocket *serverSocket = m_clientSockets.value(clientSocket);

        QByteArray data = clientSocket->readAll();
        serverSocket->write(data);
    }

    void onServerReadyRead() {
        QTcpSocket *serverSocket = qobject_cast<QTcpSocket *>(sender());
        QTcpSocket *clientSocket = m_serverSockets.value(serverSocket);

        QByteArray data = serverSocket->readAll();
        clientSocket->write(data);
    }

    void onClientDisconnected() {
        QTcpSocket *clientSocket = qobject_cast<QTcpSocket *>(sender());
        QTcpSocket *serverSocket = m_clientSockets.value(clientSocket);

        m_clientSockets.remove(clientSocket);
        m_serverSockets.remove(serverSocket);

        clientSocket->deleteLater();
        serverSocket->deleteLater();
    }

    void onServerDisconnected() {
        QTcpSocket *serverSocket = qobject_cast<QTcpSocket *>(sender());
        QTcpSocket *clientSocket = m_serverSockets.value(serverSocket);

        m_serverSockets.remove(serverSocket);
        m_clientSockets.remove(clientSocket);

        serverSocket->deleteLater();
        clientSocket->deleteLater();
    }

private:
    QMap<QTcpSocket *, QTcpSocket *> m_clientSockets;
    QMap<QTcpSocket *, QTcpSocket *> m_serverSockets;
};

在上述代码中，QTcpServer的incomingConnection()函数会在有新的客户端连接时被调用。在该函数中，我们创建了客户端的QTcpSocket实例和目标服务器的QTcpSocket实例，并将其连接起来，同时将两个QTcpSocket实例的readyRead()信号与对应的槽函数相连接。此外，我们还需要处理QTcpSocket实例的disconnected()信号。

注意：上述示例代码中的target_host和target_port需要根据实际情况进行修改。