用qt写一个socket代理代码实现两个上位机同时连接两个下位机，并将下位机的数据在两台上位机上呈现出来

下面是一个简单的 Qt socket 代理示例，可以实现两个上位机同时连接两个下位机，并将下位机的数据在两台上位机上呈现出来：

#include <QtNetwork>
#include <QtWidgets>

class SocketProxy : public QObject
{
    Q_OBJECT

public:
    SocketProxy(QObject *parent = nullptr)
        : QObject(parent)
    {
        // 创建两个下位机连接
        m_downstreamHost1 = new QTcpServer(this);
        m_downstreamHost1->listen(QHostAddress::LocalHost, 1234);
        connect(m_downstreamHost1, &QTcpServer::newConnection, this, &SocketProxy::handleDownstreamHost1Connection);

        m_downstreamHost2 = new QTcpServer(this);
        m_downstreamHost2->listen(QHostAddress::LocalHost, 1235);
        connect(m_downstreamHost2, &QTcpServer::newConnection, this, &SocketProxy::handleDownstreamHost2Connection);

        // 创建两个上位机连接
        m_upstreamHost1 = new QTcpSocket(this);
        connect(m_upstreamHost1, &QTcpSocket::readyRead, this, &SocketProxy::handleUpstreamHost1Data);
        connect(m_upstreamHost1, &QTcpSocket::disconnected, this, &SocketProxy::handleUpstreamHost1Disconnection);

        m_upstreamHost2 = new QTcpSocket(this);
        connect(m_upstreamHost2, &QTcpSocket::readyRead, this, &SocketProxy::handleUpstreamHost2Data);
        connect(m_upstreamHost2, &QTcpSocket::disconnected, this, &SocketProxy::handleUpstreamHost2Disconnection);
    }

private slots:
    void handleDownstreamHost1Connection()
    {
        // 当下位机1连接时，创建一个上位机1连接到下位机1
        QTcpSocket *downstreamSocket = m_downstreamHost1->nextPendingConnection();

        m_downstreamSockets[downstreamSocket] = 1;

        m_upstreamHost1->connectToHost(QHostAddress::LocalHost, 1236);
        if (!m_upstreamHost1->waitForConnected()) {
            qDebug() << "Failed to connect to upstream host 1";
            return;
        }

        m_upstreamSockets[m_upstreamHost1] = downstreamSocket;
    }

    void handleDownstreamHost2Connection()
    {
        // 当下位机2连接时，创建一个上位机2连接到下位机2
        QTcpSocket *downstreamSocket = m_downstreamHost2->nextPendingConnection();

        m_downstreamSockets[downstreamSocket] = 2;

        m_upstreamHost2->connectToHost(QHostAddress::LocalHost, 1237);
        if (!m_upstreamHost2->waitForConnected()) {
            qDebug() << "Failed to connect to upstream host 2";
            return;
        }

        m_upstreamSockets[m_upstreamHost2] = downstreamSocket;
    }

    void handleUpstreamHost1Data()
    {
        // 将上位机1的数据转发到下位机1
        QTcpSocket *upstreamSocket = qobject_cast<QTcpSocket*>(sender());
        if (!upstreamSocket)
            return;

        QTcpSocket *downstreamSocket = m_upstreamSockets.value(upstreamSocket);
        if (!downstreamSocket)
            return;

        QByteArray data = upstreamSocket->readAll();
        downstreamSocket->write(data);
    }

    void handleUpstreamHost2Data()
    {
        // 将上位机2的数据转发到下位机2
        QTcpSocket *upstreamSocket = qobject_cast<QTcpSocket*>(sender());
        if (!upstreamSocket)
            return;

        QTcpSocket *downstreamSocket = m_upstreamSockets.value(upstreamSocket);
        if (!downstreamSocket)
            return;

        QByteArray data = upstreamSocket->readAll();
        downstreamSocket->write(data);
    }

    void handleUpstreamHost1Disconnection()
    {
        // 断开上位机1连接时，同时断开下位机1连接
        QTcpSocket *upstreamSocket = qobject_cast<QTcpSocket*>(sender());
        if (!upstreamSocket)
            return;

        QTcpSocket *downstreamSocket = m_upstreamSockets.value(upstreamSocket);
        if (!downstreamSocket)
            return;

        m_downstreamSockets.remove(downstreamSocket);
        m_upstreamSockets.remove(upstreamSocket);

        downstreamSocket->disconnectFromHost();
        upstreamSocket->deleteLater();
    }

    void handleUpstreamHost2Disconnection()
    {
        // 断开上位机2连接时，同时断开下位机2连接
        QTcpSocket *upstreamSocket = qobject_cast<QTcpSocket*>(sender());
        if (!upstreamSocket)
            return;

        QTcpSocket *downstreamSocket = m_upstreamSockets.value(upstreamSocket);
        if (!downstreamSocket)
            return;

        m_downstreamSockets.remove(downstreamSocket);
        m_upstreamSockets.remove(upstreamSocket);

        downstreamSocket->disconnectFromHost();
        upstreamSocket->deleteLater();
    }

private:
    QTcpServer *m_downstreamHost1;
    QTcpServer *m_downstreamHost2;
    QTcpSocket *m_upstreamHost1;
    QTcpSocket *m_upstreamHost2;

    QMap<QTcpSocket*, QTcpSocket*> m_upstreamSockets;
    QMap<QTcpSocket*, int> m_downstreamSockets;
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    SocketProxy socketProxy;
    return app.exec();
}

#include "main.moc"

这个示例中，我们创建了两个下位机连接（m_downstreamHost1 和 m_downstreamHost2），分别在本地主机的端口 1234 和 1235 上监听。当下位机连接时，我们创建一个代表上位机连接的 QTcpSocket，连接到本地主机的端口 1236 和 1237，这些端口上的服务将会与下位机连接。

我们在两个上位机连接（m_upstreamHost1 和 m_upstreamHost2）上监听数据和断开事件。当上位机发来数据时，我们将数据转发到相应的下位机连接中。

当上位机连接断开时，我们同时关闭相应的下位机连接，并从 m_upstreamSockets 和 m_downstreamSockets 映射中删除相应的条目。

请注意，这只是一个示例，你需要根据你的实际需求进行调整。例如，你可能需要添加一些错误处理代码来处理连接错误，或者添加一些界面元素来显示连接状态。