UDP发广播给所有网卡（包含虚拟网卡）

//给所有网卡发广播
QList<QNetworkInterface> networkinterfaces = QNetworkInterface::allInterfaces();
foreach (QNetworkInterface interface, networkinterfaces)
{
    foreach (QNetworkAddressEntry entry, interface.addressEntries())
    {
        QHostAddress broadcastAddress = entry.broadcast();
        if (broadcastAddress != QHostAddress::Null
              && entry.ip() != QHostAddress::LocalHost
              && entry.ip().protocol() == QAbstractSocket::IPv4Protocol
            )
        {
            udpSocketServer.writeDatagram(datagram, broadcastAddress, 13999);  // UDP 发送数据
         }
     }
}

可以把其中的onServerSendBroadcast（）函数用以下函数替换一下，就可以给机器内所有网卡发广播了

void UDPServerAndClient::onServerSendBroadcast()
{
    QByteArray datagram;
    QDataStream out(&datagram, QIODevice::WriteOnly);
    out.setVersion(QDataStream::Qt_5_6);
    out << QDateTime::currentDateTime() << QHostInfo::fromName(QHostInfo::localHostName()).addresses().last().toString();
    
  //给所有网卡发广播
    QList<QNetworkInterface> networkinterfaces = QNetworkInterface::allInterfaces();
    foreach (QNetworkInterface interface, networkinterfaces)
    {
      foreach (QNetworkAddressEntry entry, interface.addressEntries())
      {
          QHostAddress broadcastAddress = entry.broadcast();
          if (broadcastAddress != QHostAddress::Null
                && entry.ip() != QHostAddress::LocalHost
                && entry.ip().protocol() == QAbstractSocket::IPv4Protocol
              )
          {
                udpSocketServer.writeDatagram(datagram, broadcastAddress, 13999);  // UDP 发送数据
          }
      }
     }
}