QTcpSocket transaction not working properly

maydin

I send data from my Android application written in Qt. I simply send messages from server (Android app) to client (desktop app) using this: client->write(data);

My slot connected to ReadyRead was like this:

void Client::readResponse() {
  auto response = tcpSocket->readAll();
  emit incomingMessage(response);
}

I saw from debugger that data comes in 2 different reads which causes incomingMessage signal emitted twice. Therefore I decided to use transactions and changed code to this:

void Client::readResponse() {
  in.startTransaction();

  QByteArray response;
  in >> response;

  if (!in.commitTransaction())
    return;

  incomingMessage(response);
}

But now, I cannot even read short messages. It was working with old code if message is short but It just doesn't work now. What do I do wrong?

Threads I found related to this:
https://forum.qt.io/topic/83969/how-to-handle-socket-transactions-uncommitted
https://forum.qt.io/topic/103794/qudpsocket-and-qdatastream
https://stackoverflow.com/questions/47740923/qtcpsocket-data-arrives-late

Christian Ehrlicher

When you want to use QDataStream on the reader side you also have to use it on the sender side.

VRonin

Maybe this example might be helpful: https://wiki.qt.io/WIP-How_to_create_a_simple_chat_application