@JonB sorry for late reply. you suggestion worked well. i followed https://wiki.qt.io/WIP-How_to_create_a_simple_chat_application and modified my code according to that. now at sender side looks like this QJsonDocument doc1; QFile j("/home/first.JSON"); if(j.exists()) { if(j.open(QIODevice:: ReadOnly| QIODevice::Text)) { jstr=j.readAll(); doc1= QJsonDocument::fromJson(jstr.toUtf8()); } j.close(); QDataStream clientStream(socket); clientStream.setVersion(QDataStream::Qt_5_7); // Create the JSON we want to send QJsonObject message; message[QStringLiteral("type")] = QStringLiteral("message"); clientStream << QJsonDocument(doc1).toJson(); } } else { ui->l_err->show(); ui->l_err->setText("Connection refused. Please check server."); } and used server application from the link above at receiver end. this works well. I have tested this with JSON file having 3000 object. Will this work for 50,000 samples and more possibly 1500000 objects?

I have these versions . It does not work when i build directly on raspberry pi .

@iman4k I don't know, I'm not a cross compile expert by any means. I'm just telling you want I can see from the configure you posted. Anyway, should be easy enough to add according to this https://doc.qt.io/qt-5/qtvirtualkeyboard-build.html you can simply open the qtvirtualkeyboard source project with QtCreator and compile it, using your cross compile kit

@bublee_jessie And what is the problem? On the server side check the client IP which is trying to connect and only accept connection if correct IP and not connected yet.

@aha_1980 ok, i understood what you said.

@vishbynature said in Qt Program start on bootup and start GUI interaction automatically: As soon as MainWindow GUI appears I should start SPI data transfer. Sure. You can use QTimer to trigger the transfer.

@dheerendra That is the content found in an archive dowload from November 2017. I have just checked the qmake.conf is from 2. October 2017 Therefore no changes from my side.