I am not getting any more errors but m_reply->readAll() now returns an empty string
From what I read in the docs about QNetworkReply, the finished() signal is emitted after the put() request is completely done. So by the time you see that, all of the reply has been sent and there is nothing more to read.

I think what you need to do is the handle the QIODevice::readyRead() signal and in your slot retrieve all of the pending data and put it onto the end of a buffer. Keep doing that until you receive the finished() signal, at which point you know you have received everything the server is going to send.