用qt写一段socket代理层的代码实现两个上位机同时连接一个下位机，并将下位机的数据呈现在两台上位机上

好的，我可以为您提供一份简单的 Qt Socket 代理层的代码，实现两个上位机同时连接一个下位机，并将下位机的数据呈现在两台上位机上。以下是代码示例：

#include <QtNetwork>
#include <QtCore>

class Proxy : public QObject
{
    Q_OBJECT

public:
    Proxy(QObject *parent = nullptr)
        : QObject(parent)
        , m_downstreamSocket(new QTcpSocket(this))
    {
        // Connect downstreamSocket signals
        connect(m_downstreamSocket, &QTcpSocket::readyRead, this, &Proxy::onDownstreamReadyRead);
        connect(m_downstreamSocket, &QTcpSocket::disconnected, this, &Proxy::onDownstreamDisconnected);
    }

    void setDownstreamHost(const QString &host, quint16 port)
    {
        m_downstreamHost = host;
        m_downstreamPort = port;
    }

    void addUpstreamConnection(QTcpSocket *socket)
    {
        // Connect upstreamSocket signals
        connect(socket, &QTcpSocket::readyRead, this, &Proxy::onUpstreamReadyRead);
        connect(socket, &QTcpSocket::disconnected, this, &Proxy::onUpstreamDisconnected);

        // Add the upstream socket to the list
        m_upstreamSockets.append(socket);

        // If this is the first upstream socket, connect to the downstream host
        if (m_upstreamSockets.count() == 1) {
            m_downstreamSocket->connectToHost(m_downstreamHost, m_downstreamPort);
        }
    }

private slots:
    void onDownstreamReadyRead()
    {
        // Forward the downstream data to all upstream sockets
        for (QTcpSocket *socket : qAsConst(m_upstreamSockets)) {
            socket->write(m_downstreamSocket->readAll());
        }
    }

    void onDownstreamDisconnected()
    {
        // Disconnect all upstream sockets
        for (QTcpSocket *socket : qAsConst(m_upstreamSockets)) {
            socket->disconnectFromHost();
        }
    }

    void onUpstreamReadyRead()
    {
        // Forward the upstream data to the downstream socket
        QTcpSocket *socket = qobject_cast<QTcpSocket*>(sender());
        if (socket) {
            m_downstreamSocket->write(socket->readAll());
        }
    }

    void onUpstreamDisconnected()
    {
        // Remove the upstream socket from the list
        QTcpSocket *socket = qobject_cast<QTcpSocket*>(sender());
        if (socket) {
            m_upstreamSockets.removeOne(socket);
        }

        // If there are no more upstream sockets, disconnect from the downstream host
        if (m_upstreamSockets.isEmpty()) {
            m_downstreamSocket->disconnectFromHost();
        }
    }

private:
    QString m_downstreamHost;
    quint16 m_downstreamPort;
    QTcpSocket *m_downstreamSocket;
    QList<QTcpSocket*> m_upstreamSockets;
};

这个代理层有一个下游套接字 `m_downstreamSocket` 和多个上游套接字 `m_upstreamSockets`。当下游套接字连接到下位机时，所有的上游套接字都将连接到代理层。当下游套接字收到数据时，代理层将数据转发到所有上游套接字。当一个上游套接字断开连接时，它将从上游套接字列表中删除。如果没有上游套接字，代理层将断开与下位机的连接。

要使用此代理层，请在您的主应用程序中创建一个 `Proxy` 对象，并使用 `setDownstreamHost()` 设置下游主机和端口。每当您的应用程序接受一个新的上游套接字时，调用 `addUpstreamConnection()` 将其添加到代理层中。

希望这可以帮助您完成您的项目！