On Tue, 12 Mar 2019, Tatsuro MATSUOKA wrote:
[...]
>> From: Mark Geisert
>> If it's not too much trouble, could you show what you tell gnuplot and how
>> you
>> set up the Qt environment?  Are you running gnuplot from inside qterminal?
>>
>> ..mark
> For qt graphics
> gnuplot.exe uses driver process named gnuplot_qt.exe.
>
> gnuplot.exe tries connect with gnuplot_qt.exe
> by
>
>
> qt->socket.connectToServer(server);
>
>
> in gnuplot.exe code but fails to connect with gnuplot_qt.exe.

Yes, I understand that is happening at a low level.  What exactly are you 
typing at your keyboard to make gnuplot produce the Qt graphics?  I would 
like to reproduce your issue on my system; what do I need to do?

Please refer to the specific questions I was asking above.
Thank you,

..mark