用qt写一段代码通过socket实现三台上位机都能对下位机进行控制，但不是同时控制。 同一时刻只能有一台在控制，但三台能同时读下位机的数据功能

以下是一个基本的代码示例，实现了三个上位机通过 socket 连接到下位机，并可以控制和读取数据。在此示例中，只有一个上位机可以控制下位机，其他两个上位机只能读取下位机的数据。您可以根据自己的需求进行修改。

// server.cpp

#include <QtNetwork>
#include <QTcpServer>
#include <QTcpSocket>

QTcpServer *server;
QTcpSocket *socket1;
QTcpSocket *socket2;
QTcpSocket *socket3;

void readSocketData()
{
    QTcpSocket *socket = qobject_cast<QTcpSocket *>(sender());
    QByteArray data = socket->readAll();
    // 处理读取到的数据
}

void acceptConnection()
{
    QTcpSocket *socket = server->nextPendingConnection();
    if (!socket1) {
        socket1 = socket;
        QObject::connect(socket1, SIGNAL(readyRead()), readSocketData);
        QObject::connect(socket1, SIGNAL(disconnected()), socket1, SLOT(deleteLater()));
        socket1->write("You are controlling the device.\n");
    } else if (!socket2) {
        socket2 = socket;
        QObject::connect(socket2, SIGNAL(readyRead()), readSocketData);
        QObject::connect(socket2, SIGNAL(disconnected()), socket2, SLOT(deleteLater()));
        socket2->write("You can only read data from the device.\n");
    } else if (!socket3) {
        socket3 = socket;
        QObject::connect(socket3, SIGNAL(readyRead()), readSocketData);
        QObject::connect(socket3, SIGNAL(disconnected()), socket3, SLOT(deleteLater()));
        socket3->write("You can only read data from the device.\n");
    } else {
        socket->write("The device is currently being controlled.\n");
        socket->close();
        socket->deleteLater();
    }
}

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

    server = new QTcpServer();
    QObject::connect(server, SIGNAL(newConnection()), acceptConnection);

    if (!server->listen(QHostAddress::Any, 1234)) {
        qDebug() << "Failed to start server.";
        return 1;
    }

    qDebug() << "Server started.";

    return app.exec();
}

// client.cpp

#include <QtNetwork>
#include <QTcpSocket>

QTcpSocket *socket;

void readSocketData()
{
    QByteArray data = socket->readAll();
    // 处理读取到的数据
}

void connectToServer()
{
    socket = new QTcpSocket();
    QObject::connect(socket, SIGNAL(readyRead()), readSocketData);
    QObject::connect(socket, SIGNAL(disconnected()), qApp, SLOT(quit()));
    socket->connectToHost("localhost", 1234);
}

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

    connectToServer();

    return app.exec();
}