Bump Qt version 5.9 to support multi-homed devices

[beeka]

qmdnsengine/CMakeLists.txt

Line 24 in c6d944d

find_package(Qt5Network 5.4 REQUIRED)

There is a bug in versions of Qt earlier than 5.9 where QUdpSocket::joinMulticastGroup() does not cope with multi-homed devices [QTBUG-27641]. I suggest bumping the minimum version to a least 5.9 to avoid the issue.

[KonstantinRitt]

Could be closed as the fix has been back-ported to 5.6 by https://codereview.qt-project.org/c/qt/qtbase/+/206577

[beeka]

The comments on that thread end with "Requestor accepts it doesn't belong in 5.6" so figured it worth checking the code has actually been incorporated into 5.6 before closing.

The latest 5.6 tag I can find is for v5.6.3 which was made on 20th Sep 2017... this is five days before the proposed back-port was done. The change doesn't appear to be in the related file in github either.

It is possible the change has been back-ported to a version between 5.6 and 5.9.... Once that is confirmed, the CMakeLists.txt would still be out of date (minimum Qt version would still be > 5.4 for reliable use).

[KonstantinRitt]

(Blind me) you're right - the cherry-pick to 5.6 has been abandoned.

Once that is confirmed, the CMakeLists.txt would still be out of date (minimum Qt version would still be > 5.4 for reliable use).

The current minimum Qt version is 5.7

[beeka]

The current minimum Qt version is 5.7

In my sleepiness, I didn't notice that my clicking on the link in my comment took me to the specific version of the CMakeLists.

Just checked and the change didn't go into 5.7. Technically, it went into the 5.8 git branch but after the only release made of 5.8... so looks like 5.9 is the earliest version with this published.