qt实现广播搜索网络地址并通过tcp连接

实现这个功能需要以下步骤：

1. 获取本机的IP地址和子网掩码，并计算出本机所在的网络地址；
2. 创建一个UDP广播套接字，并将其绑定到本机的任意一个端口上；
3. 将套接字设置为广播模式，并设置广播地址为网络地址；
4. 使用套接字发送广播消息；
5. 等待其他设备的响应，如果有设备响应，则将其IP地址保存到一个列表中；
6. 使用TCP连接尝试连接列表中的每个IP地址，直到成功连接或者所有IP地址都尝试过。

下面是一个简单的Qt程序，演示了如何实现上述功能：

#include <QtNetwork>

class BroadcastSearch : public QObject
{
    Q_OBJECT

public:
    BroadcastSearch(QObject *parent = nullptr)
        : QObject(parent)
    {
        // 获取本机的IP地址和子网掩码
        QList<QHostAddress> ipAddresses = QNetworkInterface::allAddresses();
        foreach (const QHostAddress &address, ipAddresses) {
            if (address.protocol() == QAbstractSocket::IPv4Protocol && !address.isLoopback()) {
                m_ipAddress = address.toString();
                m_subnetMask = QNetworkAddressEntry(address, QNetworkAddress::parseSubnetMask("255.255.255.0")).subnet().toString();
                break;
            }
        }

        // 计算出本机所在的网络地址
        m_networkAddress = QNetworkAddressEntry(QHostAddress(m_ipAddress), QNetworkAddress::parseSubnetMask(m_subnetMask)).ip().toString();

        // 创建一个UDP广播套接字，并将其绑定到本机的任意一个端口上
        m_socket = new QUdpSocket(this);
        m_socket->bind(QHostAddress::Any, 0);

        // 将套接字设置为广播模式，并设置广播地址为网络地址
        m_socket->setSocketOption(QAbstractSocket::BroadcastOption, 1);
        m_socket->joinMulticastGroup(QHostAddress(m_networkAddress));

        // 发送广播消息
        QByteArray datagram = "Hello, world!";
        m_socket->writeDatagram(datagram, QHostAddress::Broadcast, 1234);

        // 等待其他设备的响应
        connect(m_socket, &QUdpSocket::readyRead, this, &BroadcastSearch::onReadyRead);
    }

signals:
    void deviceFound(const QString &ipAddress);

private slots:
    void onReadyRead()
    {
        while (m_socket->hasPendingDatagrams()) {
            QByteArray datagram;
            datagram.resize(m_socket->pendingDatagramSize());
            QHostAddress sender;
            quint16 senderPort;
            m_socket->readDatagram(datagram.data(), datagram.size(), &sender, &senderPort);

            // 将响应中的IP地址保存到列表中
            QString ipAddress = sender.toString();
            if (!m_deviceList.contains(ipAddress)) {
                m_deviceList.append(ipAddress);
                emit deviceFound(ipAddress);
            }
        }
    }

public slots:
    void connectToDevices()
    {
        foreach (const QString &ipAddress, m_deviceList) {
            QTcpSocket *socket = new QTcpSocket(this);
            socket->connectToHost(ipAddress, 5678);
            connect(socket, &QTcpSocket::connected, this, &BroadcastSearch::onConnected);
        }
    }

private slots:
    void onConnected()
    {
        QTcpSocket *socket = qobject_cast<QTcpSocket *>(sender());
        if (socket) {
            qDebug() << "Connected to" << socket->peerAddress().toString();
        }
        socket->deleteLater();
    }

private:
    QString m_ipAddress;
    QString m_subnetMask;
    QString m_networkAddress;
    QUdpSocket *m_socket;
    QStringList m_deviceList;
};

使用方法：

BroadcastSearch *search = new BroadcastSearch(this);
connect(search, &BroadcastSearch::deviceFound, this, &MyClass::onDeviceFound);
search->connectToDevices();

其中，`onDeviceFound`是一个槽函数，用来处理发现新设备的事件。