A QAbstractSocket can be close()'d at any time, independently of its
current connection state. being closed means that we cannot use it to
read or write data, but internally it might still have some data to
send or receive, for example to an http server. We can even get a
connected() signal after close()'ing the socket.
We need to catch this condition and mark any pending data not yet
written to the socket for resending.
(cherry picked from commit 0df5d07929)
Task-number: QTBUG-48326
Change-Id: I67d9ad36f7288c9c6bef51aa6253d7b187737601
Reviewed-by: Ulf Hermann <ulf.hermann@theqtcompany.com>
Reviewed-by: Markus Goetz (Woboq GmbH) <markus@woboq.com>
7aba75ffc5