用qt来实现模拟telnet客户端，并可输入数据

下面的代码演示了如何使用Qt实现模拟Telnet客户端，并且可以输入数据发送到远程服务器：

#include <QtNetwork/QAbstractSocket>
#include <QtNetwork/QHostAddress>
#include <QtNetwork/QNetworkInterface>
#include <QtNetwork/QTcpSocket>
#include <QtCore/QDebug>
#include <QtCore/QThread>
#include <QtCore/QCoreApplication>

class TelnetClient : public QObject
{
    Q_OBJECT
public:
    explicit TelnetClient(QObject *parent = nullptr);
    virtual ~TelnetClient();

    void connectToServer(const QString &host, quint16 port);
    void sendCommand(const QByteArray &command);

signals:
    void dataReceived(const QByteArray &data);

public slots:
    void onConnected();
    void onDisconnected();
    void onError(QAbstractSocket::SocketError socketError);
    void onDataReceived();

private:
    QTcpSocket *m_socket;
    QByteArray m_buffer;
};

TelnetClient::TelnetClient(QObject *parent)
    : QObject(parent)
    , m_socket(new QTcpSocket(this))
{
    connect(m_socket, &QTcpSocket::connected, this, &TelnetClient::onConnected);
    connect(m_socket, &QTcpSocket::disconnected, this, &TelnetClient::onDisconnected);
    connect(m_socket, static_cast<void(QAbstractSocket::*)(QAbstractSocket::SocketError)>(&QAbstractSocket::error), this, &TelnetClient::onError);
    connect(m_socket, &QTcpSocket::readyRead, this, &TelnetClient::onDataReceived);
}

TelnetClient::~TelnetClient()
{
    if (m_socket) {
        m_socket->close();
    }
}

void TelnetClient::connectToServer(const QString &host, quint16 port)
{
    qDebug() << "Connecting to server" << host << "on port" << port;
    m_socket->connectToHost(host, port);
}

void TelnetClient::sendCommand(const QByteArray &command)
{
    m_socket->write(command);
}

void TelnetClient::onConnected()
{
    qDebug() << "Connected to server";
}

void TelnetClient::onDisconnected()
{
    qDebug() << "Disconnected from server";
}

void TelnetClient::onError(QAbstractSocket::SocketError socketError)
{
    qDebug() << "Error:" << socketError;
}

void TelnetClient::onDataReceived()
{
    QByteArray data = m_socket->readAll();
    m_buffer.append(data);

    while (m_buffer.contains('\n')) {
        int pos = m_buffer.indexOf('\n');
        QByteArray line = m_buffer.left(pos);
        m_buffer.remove(0, pos + 1);

        // Emit a signal to notify the data received
        emit dataReceived(line);
    }
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    TelnetClient *client = new TelnetClient(&a);
    client->connectToServer("localhost", 23);

    // Connect a slot to the signal dataReceived
    QObject::connect(client, &TelnetClient::dataReceived, [](const QByteArray &data) {
        qDebug() << "Received data:" << data;
    });

    // Start the event loop
    return a.exec();
}

在main函数中，创建了一个TelnetClient对象，并连接到本地主机的Telnet服务器。然后通过connect函数将TelnetClient对象的dataReceived信号连接到一个lambda函数，当从服务器接收到数据时，会触发dataReceived信号，并且lambda函数会被调用，打印接收到的数据。

此外，还可以使用TelnetClient对象的sendCommand函数向服务器发送数据。例如，可以在命令行中输入数据并发送：

QString command;
while (true) {
    std::cout << "Enter command: ";
    std::cin >> command;
    client->sendCommand(command.toUtf8());
}

这样就可以在命令行中输入数据并发送到远程服务器了。