I have an open kde plasma session on the desktop. So far so good. Now i want to
open a second parallel kde plasma session, e.g. with nomachine's nx. That fails
with the message:

Loading stage  "initial" 64
startkde: Starting up...
kdeinit5: preparing to launch 'libkdeinit5_klauncher'
kdeinit5: Launched KLauncher, pid = 9707, result = 0
Waiting for already running klauncher to exit.
Waiting for already running klauncher to exit.
Another instance of klauncher is already running!
kdeinit5: Communication error with launcher. Exiting!
kdeinit5_wrapper: Warning: connect(/run/user/631/kdeinit5__0) failed: :
Connection refused
Qt: Session management error: networkIdsList argument is NULL
Configuring Lock Action
XSync seems available and ready
XSync Inited
Supported, init completed
Created alarm 23068673
ksmserver: "/run/user/631/KSMserver"
ksmserver: KSMServer: SetAProc_loc: conn  0 , prot= local , file=
@/tmp/.ICE-unix/9709
ksmserver: KSMServer: SetAProc_loc: conn  1 , prot= unix , file=
/tmp/.ICE-unix/9709
ksmserver: KSMServer::restoreSession  "saved at previous logout"
startkde: Shutting down...
kdeinit5_wrapper: Warning: connect(/run/user/631/kdeinit5__0) failed: :
Connection refused
Error: Can not contact kdeinit5!
startkde: Done.
Qt: Session management error: Could not open network socket
The X11 connection broke (error 1). Did the X11 server die?


The rason is that the first kde plasma session has opened the socket
/run/user/631/kdeinit5__0 (631 is my uid), and the second kde plasma from nx
wants to open the same, which is already blocked by the first session. Closing
the first kde plasma makes the nx work.
A workaround would be using another window manager for the second session.

Is there a trick withing kde plasma to make both sessions work in parallel? Or
is there a bug?

On opensuse 13.2 and ealier (plasma 4) this never was a problem, because in
/run/user/631/ksocket-ulrich/ there were in such cases two sockets opened,
e.g.: kdeinit4__0 and kdeinit4_nx.mpia-hd.mpg.de_516

With kind regards, ulrich