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
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?