Bug: opencv failed when imshow after receving from socket

[wangyihuan123]

Server:
sudo python server.py
Waiting connections...
[+] New server socket thread started for 127.0.0.1:57814
((921600,), 0)
('frame', (480, 640, 3))
QObject::moveToThread: Current thread (0x7feffc001370) is not the object's thread (0x7feffc053c70).
Cannot move to target thread (0x7feffc001370)

Segmentation fault (core dumped)

Client:
python client.py
('Frame: ', 1)
[Error] [Errno 32] Broken pipe
[Error] [Errno 32] Broken pipe
[Error] [Errno 32] Broken pipe
[Error] [Errno 32] Broken pipe

[wangyihuan123]

This is because of Qt.

The openCv author says that this problem comes from different Qt versions in openCv and the linux distro. That is: openCv comes with Qt4, but Qt5 is already installed.

Solution:
I created a new conda environment and installed opencv and pyqt.
Then remove libqt5x11extras5 libqt5x11extras5-dev via apt-get.
Now it works!

Why:
I probably installed libqt5x11extras5 libqt5x11extras5-dev these libs when I install ROS denpendencies.

Check these for detail:
opencv/opencv-python#46 and https://stackoverflow.com/questions/46449850/how-to-fix-the-error-qobjectmovetothread-in-opencv-in-python