以下是获取通信对等方的MAC地址的代码.
在后台，它使用Windows命令 arp .
使用在Windows 7上测试过的Qt5.8:

Here is the code to get the MAC address of the communication peer.
Under the hood, it uses the Windows command arp.
Using Qt5.8, tested on Windows 7:

QString getMacForIP(QString ipAddress)
{
    QString MAC;
    QProcess process;
    //
    process.start(QString("arp -a %1").arg(ipAddress));
    if(process.waitForFinished())
    {
        QString result = process.readAll();
        QStringList list = result.split(QRegularExpression("\\s+"));
        if(list.contains(ipAddress))
            MAC = list.at(list.indexOf(ipAddress) + 1);
    }
    //
    return MAC;
}

备注:远程对等方必须位于同一LAN上.
另一点注意:如果IP地址不存在，您将获得一个用于MAC的空字符串.

Remark: remote peer must be on the same LAN.
Another remark: you'll get an empty string for MAC if the IP address is not present.