send data from QUDPsocket c++ to QML UI fail

[Xuan Trieu]

i try send data from UDPsocket to QMl with timer 1s but it not working.
udp.h

#ifndef UDP_H
#define UDP_H

#include <QObject>
#include <QUdpSocket>

class UDP : public QObject
{
    Q_OBJECT
    Q_PROPERTY(QString convert READ receiverdata);
public:
    explicit UDP(QObject *parent = nullptr);
    QString convert;

signals:
public slots:
    QString receiverdata();
private:
    QUdpSocket *socket;

};

#endif // UDP_H

udp.cpp

#include "udp.h"
#include <iostream>
UDP::UDP(QObject *parent)
    : QObject{parent}
{
    socket = new QUdpSocket(this);
    socket->bind(QHostAddress::AnyIPv4,5005);
    connect(socket,SIGNAL(readyRead()),this,SLOT(receiverdata()));
}

QString UDP::receiverdata()
{
    QByteArray Buffer;
    Buffer.resize(socket->pendingDatagramSize());
    QHostAddress sender;
    quint16 senderPort;
    socket->readDatagram(Buffer.data(),Buffer.size(),&sender,&senderPort);
    qDebug() << "message: "<< QString(Buffer);
    convert = QString(Buffer);
    return convert;
}

main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include "someclass.h"
#include <QQmlContext>
#include "udp.h"
int main(int argc, char *argv[])
{
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif
    QGuiApplication app(argc, argv);
    UDP server;
    QString convert;
    convert = server.receiverdata();
    QQmlApplicationEngine engine;
    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject *obj, const QUrl &objUrl) {
        if (!obj && url == objUrl)
            QCoreApplication::exit(-1);
    }, Qt::QueuedConnection);
    engine.load(url);
    QQmlContext * rootContext = engine.rootContext();
    rootContext -> setContextProperty("UDP",&server);


    return app.exec();
}

main.qml

import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.15
Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")
    Text {
        id: text1
        text: qsTr("text")
    }
    Timer{
        interval: 1000
        running: true
        repeat: true
        onTriggered: text1.text = UDP.receiverdata();
    }
}

Application output:
message: ""
message: "30"
message: ""
message: "26"
message: ""
message: "29"
message: ""
message: "68"
message: ""
message: "36"
message: ""
message: "13"
message: ""
message: "78"

when timer run, message will be "". i don't understand it.
pl help me, thank you.