When the read buffer has a max size we do our best not to exceed it. Usually there's no problem and we just read more when the next tcp frame arrives. However if there's data leftover after the last tcp frame arrived then we won't receive any more data. To counter this QSslSocket would try to invoke QSslSocketPrivate::transmit indirectly if there were any bytes available on the plain socket. The problem is that with Schannel the last few remaining bytes would not be in the plain socket, but in the 'intermediateBuffer'. So let's make QSslSocket aware of that. Fixes: QTBUG-90625 Change-Id: If56e4cce558f99c9a08a1f6818e005a887712ef2 Reviewed-by: Edward Welbourne <edward.welbourne@qt.io> Reviewed-by: Norbert Pfeiler <norbert.pfeiler+git@gmail.com> Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io> (cherry picked from commit 6d4da1340f18b66e60ed6969aeb7180e00d39077) Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>