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Qjackctl 4.5.0 starts jack server but applications cannot connect to it

My Ubuntu 16.04 just updated to Qjackctl 4.5.0 and this is what happened:
Starting Qjackctl seems to work well as it does before updating and I can see the jackdbus and it's PID running from the command line.
But Qjackctl's scripting line "read script after start: a2jmidid -e &" (or even /usr/bin/a2jmidid -e &) isn't working.
And although jackdbus is up and running, applications like patchage or audacity are not connected to it.
So, I have to shutdown Qjackctl and kill Jackdbus.
Then I start Jackd from the command line with "jackd -d alsa -d hw:2 -p 128 -r 44100" which works fine.
I open a second console and do "a2jmidid -e &" which also works fine.
Now patchage and audacity are connected to the jackserver and I can work as I did before 4.5.0. - The only difference is, that I don't have portaudio (but I don't miss it :-)).
Any idea why Qjackctl 4.5.0 starts the jackdbus in this "hidden mode", so that no application can connect to it?


rncbc's picture

Try not work with jackdbus from qjacktl: turn off Setup/Misc/Other/Enable JACK D-Bus interface; killall jackd that might be possibly running; killall jackdbus as well; start qjackctl and try now again.

Also look for some error our suspicious evidences on the messages window

One question though: where did you get that newer qjackctl v0.4.5 from? Is that from regular ubuntu16.04 universe?

Disabling jackdbus had no effect.
There have been some "couldn't connect to client" messages, I think...
I have Ubuntu Studio 16.04 with the kxstudio repos bound in. It has been the kxstudio version. Maybe that was the point.
Uninstalled the kx version and tried to compile 0.4.5 from the sources. No success. Probably because of the dependencies. There were some ugly looking "no's" when I did ./configure:

checking for qmake-qt5... no
checking for ALSA... no
configure: WARNING: *** ALSA library not found.
checking for PORTAUDIO... no
configure: WARNING: *** PORTAUDIO library not found.
checking CoreAudio/CoreAudio.h usability... no
checking CoreAudio/CoreAudio.h presence... no
checking for CoreAudio/CoreAudio.h... no
checking for QT5X11EXTRAS... no
JACK Version support (JACK2) . . . . . . . . . . .: no
ALSA MIDI Sequencer support . . . . . . . . . . .: no
PortAudio interface support . . . . . . . . . . .: no
CoreAudio interface support . . . . . . . . . . .: no
X11 Unique/Single instance . . . . . . . . . . . .: no
Debugger stack-trace (gdb) . . . . . . . . . . . .: no

I gave up this, started Synaptic and forced the installation of Ubuntu Qjackctl 0.4.2 which worked fine (including Portaudio, Pulseaudio and a2jmidid script).
I know it's poor, but that's Ok for me :-)

Thanx and kind regards from Hamburg,


i've same problem with Ubuntu 18.04 which i updated to ubuntustudio using official repositories.

With Ubuntu 18.04 comes Qjackctl 0.4.5. I tried the AppImage 0.5.5 but had the same behavior: The Qjackctl application displays in message window that jack is started but no jack applications can connect to the jack server.

When i start the daemon manually "jackd ..." it works.

So i installed the Qjackctl 0.4.2 version as suggested which works fine.


rncbc's picture

i'd ask you please to start from scratch: backup and/or just remove the configuration file (~/.config/; then try again.
also try to re-install either jackd *or* jackdbus, but not both: never have more than one installed at any single time;

if this is all too scary for you, then i'm afraid none of us (you and me) can help each other in any way: so please goo luck sticking with bit-rotten v0.4.2


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