问QTcpSocket未知误差

EN

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);

    tcpSocket = new QTcpSocket(this);

    connect(tcpSocket, SIGNAL(connected()), this, SLOT(connected()));

    QHostAddress ha;
    ha.setAddress("myIP");

    tcpSocket->connectToHost(ha, 6401);

    if(!tcpSocket->waitForConnected(3000)) {
        ui->lineEdit->setText(tcpSocket->errorString());
    }
    else
        ui->lineEdit->setText("connected");
}

void Widget::connected()
{
   tcpSocket->write("hello this is client\r\n");
   tcpSocket->flush();
   tcpSocket->waitForBytesWritten(3000);

    tcpSocket->close();
}

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);

    tcpServer = new QTcpServer(this);

    connect(tcpServer, SIGNAL(newConnection()), this, SLOT(newConnection()));

    if(!tcpServer->listen(QHostAddress::Any, 6401)) {
           ui->lineEdit->setText("server not started");
       }
       else
           ui->lineEdit->setText("server started");
}

void Widget::newConnection()
{
    QTcpSocket *tcpSocket= tcpServer->nextPendingConnection();

    qDebug() << tcpSocket->readAll();
    tcpSocket->waitForReadyRead(3000);

    tcpSocket->close();
}