用qt写一段代码实现两个上位机通过代理连接两个下位机，两个下位机收到命令后会发送的数据，发送的数据会在两台上位机上同时显示出来

好的，以下是一个简单的实现思路和代码示例：

1. 在Server端建立一个TCP服务器，等待Client的连接请求，代码如下：

QTcpServer *server = new QTcpServer(this);
connect(server, &QTcpServer::newConnection, this, &Server::handleNewConnection);
if (!server->listen(QHostAddress::Any, 1234)) {
    qCritical() << "Failed to start server!";
    return;
}
qInfo() << "Server started listening on port 1234!";

2. 在Server的handleNewConnection槽函数中，接受Client的连接请求，并为其创建一个QTcpSocket，代码如下：

void Server::handleNewConnection() {
    QTcpSocket *clientSocket = server->nextPendingConnection();
    connect(clientSocket, &QTcpSocket::readyRead, this, &Server::handleReadyRead);
    connect(clientSocket, &QTcpSocket::disconnected, clientSocket, &QObject::deleteLater);
    qInfo() << "Client connected!";
}

3. 在Client端，建立一个QTcpSocket，通过代理连接Server，代码如下：

QNetworkProxy proxy;
proxy.setType(QNetworkProxy::Socks5Proxy);
proxy.setHostName("proxy.example.com");
proxy.setPort(1080);
QNetworkProxy::setApplicationProxy(proxy);

QTcpSocket *socket = new QTcpSocket(this);
connect(socket, &QTcpSocket::readyRead, this, &Client::handleReadyRead);
connect(socket, &QTcpSocket::disconnected, this, &QObject::deleteLater);
socket->connectToHost("server.example.com", 1234);
if (!socket->waitForConnected()) {
    qCritical() << "Failed to connect to server!";
    return;
}
qInfo() << "Connected to server!";

4. 在Server端的handleReadyRead槽函数中，接收Client发送的命令，将命令发送给两个下位机，并等待下位机的回复，代码如下：

void Server::handleReadyRead() {
    QTcpSocket *clientSocket = qobject_cast<QTcpSocket *>(sender());
    QDataStream in(clientSocket);
    while (in.device()->bytesAvailable() > 0) {
        QByteArray command;
        in >> command;
        qInfo() << "Received command: " << command;

        // Send command to both devices
        device1Socket->write(command);
        device2Socket->write(command);

        // Wait for reply from devices
        QByteArray reply1 = device1Socket->readAll();
        QByteArray reply2 = device2Socket->readAll();

        // Send reply to client
        QByteArray reply;
        reply.append(reply1);
        reply.append(reply2);
        clientSocket->write(reply);
    }
}

5. 在Client端的handleReadyRead槽函数中，接收Server发送的数据，将数据显示在程序中，并将数据发送给另一个上位机，代码如下：

void Client::handleReadyRead() {
    QDataStream in(socket);
    while (in.device()->bytesAvailable() > 0) {
        QByteArray data;
        in >> data;
        qInfo() << "Received data: " << data;

        // Display data in UI
        ui->textEdit->append(QString::fromUtf8(data));

        // Forward data to other client
        otherClientSocket->write(data);
    }
}

注意：上面的示例代码只是一个简单的演示，实际实现中需要根据具体需求进行修改。另外，建议将连接、发送和接收等操作都放在单独的线程中进行，以免阻塞主线程。