Определить подключено ли к компьютеру устройство по протоколу Ethernet

void server::writeFile()
{
    QTcpSocket* writeFileSocket = (QTcpSocket*)sender();
    QFile file ("/home/00001-150713_a11.txt");   
    file.open(QIODevice::ReadOnly);
    QByteArray buf = file.readAll();
    writeFileSocket->write(buf, buf.size());
   writeFileSocket->flush(); 
}

void Client::readFile()
{
    QFile file("/home/my.txt");
    file.open(QIODevice::WriteOnly);
    QByteArray arrFile = tcpSocketReadFile->readAll();
    file.write(arrFile);
    file.close();
}

server::server(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::server)
{
    ui->setupUi(this);
   
    fortunes<< tr("Ready");
    connect(tcpServer, SIGNAL(newConnection()), this, SLOT(write()));
}
void server::write()
{
    QByteArray block;
    QDataStream out(&block, QIODevice::WriteOnly);
    out.setVersion(QDataStream::Qt_4_0);
 
    out << (quint16)0;
    out << fortunes.at(qrand() % fortunes.size());
    out.device()->seek(0);
    out << (quint16)(block.size() - sizeof(quint16));
 
 
    clientConnection = tcpServer->nextPendingConnection();
    connect(clientConnection, SIGNAL(disconnected()),
            clientConnection, SLOT(deleteLater()));
 
   clientConnection->write(block);
   connect(clientConnection, SIGNAL(readyRead()),this, SLOT(read()));
  
}

writeFileSocket->write(buf, buf.size());

void server::writeFile()
{
    QFile *sendFile = new QFile ("/home/150713.txt");
    
    if (sendFile->open(QIODevice::ReadOnly))
    {
        QByteArray byteArray;
        while(!sendFile->atEnd())
        {
            byteArray = sendFile->read(800);
 
            int blsize = blsize + clientConnection->write(byteArray);
      }
        ui->lineEdit_3->setText(tr("File send"));
    }
}

void Client::readFile()
{
    QFile file("/home/15071313.txt");
    file.open(QIODevice::WriteOnly);
    while(!tcpSocket->atEnd())
    {
        QByteArray data = tcpSocket->read(800);
        file.write(data);
    }
    file.close();
}

while(!tcpSocket->atEnd())
    {
        QByteArray data = tcpSocket->read(800);
        file.write(data);
    }