Qt "Session management error" on start up

[JonB]

Qt 5.7, Linux. I have an intermittent (fairly infrequent) error as the very thing which happens on starting to run my Qt application. (The fact that I use PyQt/Python should not be relevant, I understand that I'm more or less on my own in that respect.) The very first thing I see output is:

Qt: Session management error: Could not open network socket

This message happens intermittently, some days yes, some days no, there is no pattern, and has no relationship to any changes I might make in my code or not. The application actually continues to run fine. I have to restart the Linux machine for it to disappear, which is a bit pants.

Where does that Qt "Session management error" come from, why is trying to open a network socket, and what does it signify?

[jsulm]

@JonB Google told me: https://forum.qt.io/topic/77701/qt-session-management-error-could-not-open-network-socket

[JonB]

@jsulm
Yeah, I could have Googled, I spend all my time Googling others' question, I got lazy and fancied a chat about this :)

Your link takes me to https://stackoverflow.com/a/987089/489865. I don't have a hostname issue, I don't use any KDE stuff, I do use GNOME, but the find reveals no *session* files recently modified that are of any relevance. Ho-hum.

I'll just try logging off & logging on again, instead of rebooting, to see if that fixes, and report back....

[jsulm]

@JonB OK, other possibility would be to search for this string in Qt sources to see what the condition for printing this is.

[JonB]

@jsulm

1. Logging off did not clear. Rebooting did. I won't die in a ditch over this one, but I am interested as to what it is.

2. Lots of Google hits for others hitting this, no solutions/explanations (at least as applies to me).

3. I have to search online sources for Qt (I'm not C++). I believe the error comes at https://code.woboq.org/qt5/qtbase/src/plugins/platforms/xcb/qxcbsessionmanager.cpp.html#376 .

That would make it in QXcbSessionManager. What's one of those all about, OOI, please?

That function starts with:

    // avoid showing a warning message below
    if (!qEnvironmentVariableIsSet("SESSION_MANAGER"))
        return;

I don't know whether that variable is supposed to be set/clear under some circumstances so that the code error is not hit, or whether the code call is supposed to be made but should not error?

[SGaist]

Hi,

You can find more information about that variable here.

The QXXXSessionManager classes are used by application that wants to save/restore stuff on "session stop/restart". A session being started when you login to your desktop environment and stops when you logout.