WLJS randomly fails to connect to the Wolfram Kernel

[VictorSeven]

Hi,

Today I found a problem trying to connect to Wolfram Kernel. In some cases, WLJS cannot connect to kernel, complaining about a license error that as far as I know it could be anything else. Other times it loads, but it says it cannot connect to the Kernel. Other times it starts without any problem. The main problem is that today it was locked in the failing state for hours, so I could not get any work done.

I did not change anything in my computer. Yesterday it was working, today I started finding all these problems. It is true that in the past WLJS had some hiccups connecting to the kernel, but usually a restart would solve it... today it was just impossible for some random reason.

I tried to troubleshoot the issue but I didn't find any solution. Wolfram Engine works perfectly well when I call wolframscript and also in Jupyter.

My Wolfram Engine is version 14.0.0 for Linux x86 (64-bit)
WLJS is set at 2.8.9, as I updated today to see if there was any problem.

This is the log of a failing startup, which would not even open the program:

WLJS Notebooks
Copyright (c) 2025 Coffee liqueur
Licensed under the GNU GPL v3.0. See /LICENSE.md.

This product bundles third-party FOSS. 
Wolfram Engine is proprietary and distributed by Wolfram Research.
Starting wolframscript by path: wolframscript

Wolfram Language 14.0.0 Engine for Linux x86 (64-bit)
Copyright 1988-2023 Wolfram Research, Inc.
In[1]:=
This project is not affiliated with, endorsed by, or sponsored by Wolfram\
 
>   Research, Inc. Wolfram and Wolfram Language are trademarks of Wolfram\
 
>   Research, Inc.
>> WLJS Extensions >> Loaded >> wljs-api
>> WLJS Extensions >> Loaded >> wljs-cells
>> WLJS Extensions >> Loaded >> wljs-debugger
>> WLJS Extensions >> Loaded >> wljs-demos-archive
>> WLJS Extensions >> Loaded >> wljs-docs-archive
>> WLJS Extensions >> Loaded >> wljs-editor
>> WLJS Extensions >> Loaded >> wljs-excalidraw
>> WLJS Extensions >> Loaded >> wljs-export-html
>> WLJS Extensions >> Loaded >> wljs-graphics3d-threejs
>> WLJS Extensions >> Loaded >> wljs-graphics-d3
>> WLJS Extensions >> Loaded >> wljs-html-support
>> WLJS Extensions >> Loaded >> wljs-inputs
>> WLJS Extensions >> Loaded >> wljs-interpreter
>> WLJS Extensions >> Loaded >> wljs-js-support
>> WLJS Extensions >> Loaded >> wljs-magic-support
>> WLJS Extensions >> Loaded >> wljs-manipulate
>> WLJS Extensions >> Loaded >> wljs-markdown-support
>> WLJS Extensions >> Loaded >> wljs-mermaid-support
>> WLJS Extensions >> Loaded >> wljs-neuralnet
>> WLJS Extensions >> Loaded >> wljs-plotly
>> WLJS Extensions >> Loaded >> wljs-print-redirect-fix
>> WLJS Extensions >> Loaded >> wljs-revealjs
>> WLJS Extensions >> Loaded >> wljs-sharedlib-d3
>> WLJS Extensions >> Loaded >> wljs-sharedlib-mk
>> WLJS Extensions >> Loaded >> wljs-sharedlib-three
>> WLJS Extensions >> Loaded >> wljs-snippets
>> WLJS Extensions >> Loaded >> wljs-sound
>> WLJS Extensions >> Loaded >> wljs-templates
>> WLJS Extensions >> Loaded >> wljs-toc
>> WLJS Extensions >> Loaded >> wljs-video
>> WLJS Extensions >> Loaded >> wljs-wlx-support
>> WLJS Extensions >> Loaded >> wljs-wxf-accelerator
>> WLJS Extensions >> Loaded >> wljs-xterm
WLJS Notebook does not collect or transmit your data unless you explicitly\
 
>   choose a feature that needs the network.
>> CSockets >> Unix >> Linux-x86-64
>> CSockets >> Unix >> Loading UV library...
>> CSockets >> Unix >> Loading library... LLink 7
LibraryFunction::version: 
   The version number 8 of the library is not consistent with the current or
     any previous WolframLibraryVersion.
LibraryFunction::initerr: 
   A nonzero error code 7 was returned during the initialization of the
     library /opt/WLJS
     Notebook/resources/app/wl_packages/KirillBelov_CSockets/LibraryResources/
     Linux-x86-64-v7/usockets.so.
LibraryFunction::libload: 
   The function run_uvloop was not loaded from the file 
    /opt/WLJS
     Notebook/resources/app/wl_packages/KirillBelov_CSockets/LibraryResources/
     Linux-x86-64-v7/usockets.so.
>> CSockets >> Unix >> Another attempt to load v6
>> CSockets >> Unix >> Succesfully loaded! LLink
Segmentation fault (core dumped)
The Wolfram Engine exited because of a license error.
Process exited with code 139
No hup

And this one is from a successful startup, just to compare

WLJS Notebooks
Copyright (c) 2025 Coffee liqueur
Licensed under the GNU GPL v3.0. See /LICENSE.md.

This product bundles third-party FOSS. 
Wolfram Engine is proprietary and distributed by Wolfram Research.
Starting wolframscript by path: wolframscript

Wolfram Language 14.0.0 Engine for Linux x86 (64-bit)
Copyright 1988-2023 Wolfram Research, Inc.
In[1]:=
This project is not affiliated with, endorsed by, or sponsored by Wolfram\
 
>   Research, Inc. Wolfram and Wolfram Language are trademarks of Wolfram\
 
>   Research, Inc.
>> WLJS Extensions >> Loaded >> wljs-api
>> WLJS Extensions >> Loaded >> wljs-cells
>> WLJS Extensions >> Loaded >> wljs-debugger
>> WLJS Extensions >> Loaded >> wljs-demos-archive
>> WLJS Extensions >> Loaded >> wljs-docs-archive
>> WLJS Extensions >> Loaded >> wljs-editor
>> WLJS Extensions >> Loaded >> wljs-excalidraw
>> WLJS Extensions >> Loaded >> wljs-export-html
>> WLJS Extensions >> Loaded >> wljs-graphics3d-threejs
>> WLJS Extensions >> Loaded >> wljs-graphics-d3
>> WLJS Extensions >> Loaded >> wljs-html-support
>> WLJS Extensions >> Loaded >> wljs-inputs
>> WLJS Extensions >> Loaded >> wljs-interpreter
>> WLJS Extensions >> Loaded >> wljs-js-support
>> WLJS Extensions >> Loaded >> wljs-magic-support
>> WLJS Extensions >> Loaded >> wljs-manipulate
>> WLJS Extensions >> Loaded >> wljs-markdown-support
>> WLJS Extensions >> Loaded >> wljs-mermaid-support
>> WLJS Extensions >> Loaded >> wljs-neuralnet
>> WLJS Extensions >> Loaded >> wljs-plotly
>> WLJS Extensions >> Loaded >> wljs-print-redirect-fix
>> WLJS Extensions >> Loaded >> wljs-revealjs
>> WLJS Extensions >> Loaded >> wljs-sharedlib-d3
>> WLJS Extensions >> Loaded >> wljs-sharedlib-mk
>> WLJS Extensions >> Loaded >> wljs-sharedlib-three
>> WLJS Extensions >> Loaded >> wljs-snippets
>> WLJS Extensions >> Loaded >> wljs-sound
>> WLJS Extensions >> Loaded >> wljs-templates
>> WLJS Extensions >> Loaded >> wljs-toc
>> WLJS Extensions >> Loaded >> wljs-video
>> WLJS Extensions >> Loaded >> wljs-wlx-support
>> WLJS Extensions >> Loaded >> wljs-wxf-accelerator
>> WLJS Extensions >> Loaded >> wljs-xterm
WLJS Notebook does not collect or transmit your data unless you explicitly\
 
>   choose a feature that needs the network.
>> CSockets >> Unix >> Linux-x86-64
>> CSockets >> Unix >> Loading UV library...
>> CSockets >> Unix >> Loading library... LLink 7
LibraryFunction::version: 
   The version number 8 of the library is not consistent with the current or
     any previous WolframLibraryVersion.
LibraryFunction::initerr: 
   A nonzero error code 7 was returned during the initialization of the
     library /opt/WLJS
     Notebook/resources/app/wl_packages/KirillBelov_CSockets/LibraryResources/
     Linux-x86-64-v7/usockets.so.
LibraryFunction::libload: 
   The function run_uvloop was not loaded from the file 
    /opt/WLJS
     Notebook/resources/app/wl_packages/KirillBelov_CSockets/LibraryResources/
     Linux-x86-64-v7/usockets.so.
>> CSockets >> Unix >> Another attempt to load v6
>> CSockets >> Unix >> Succesfully loaded! LLink
Caching is enabled for 1 hour! Type\
 
>   JerryI`WLX`Importer`Private`CacheControl[False] to disable it
>> Checking version of WLJS Notebook ...
>> 2.8.9
>> Default paths:
>> >> QuickNotesDir: /tmp/wljs_quicknotes
>> >> BackupsDir: /tmp/wljs_backups
>> >> DefaultDocumentsDir: /home/victor/Documentos/WLJS Notebooks
>> >> DemosDir: /home/victor/Documentos/WLJS Notebooks/Demos
>> >> ExtensionsDir: /home/victor/Documentos/WLJS Notebooks/Extensions
>> >> AppDataDir: /home/victor/.config/wljs-notebook
>> >> AppConfig: /home/victor/.config/wljs-notebook/_settings.wl
>> >> Root: /opt/WLJS Notebook/resources/app
Initializing WordData indices ....
>> WLJS Extensions >> Sync deferred packages >> FrontProxy.wl
>> WLJS Extensions >> Sync deferred packages >> BoxesConverter.wl
>> WLJS Extensions >> Sync deferred packages >> WSP.wl
>> WLJS Extensions >> Sync deferred packages >> Canvas2D.wl
>> WLJS Extensions >> Sync deferred packages >> AnimationFramework
>> WLJS Extensions >> Sync deferred packages >> AnimationFramework.wl
taring HTTP server...
>> Loading packages: FRONTEND
OptionValue::nodef: Unknown option Data for Component$21020.

OptionValue::nodef: Unknown option Size for Component$21020.

OptionValue::nodef: Unknown option Ref for Component$21020.

General::stop: Further output of OptionValue::nodef
     will be suppressed during this calculation.
>> Evaluator >> Added new
>> Evaluator >> Added new
>> Evaluator >> Added new
>> Evaluator >> Added new
>> Evaluator >> Added new
>> Evaluator >> Added new
>> Evaluator >> Added new
>> Evaluator >> Added new
>> Evaluator >> Added new
>> Evaluator >> Added new
>> Evaluator >> Added new
>> Evaluator >> Added new
>> Evaluator >> Added new
>> Evaluator >> Added new
>> Note: wljs-docs-archive only redirects to a web page since 2.8.1
>> Snippets >> Library loading...
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/camera.wln
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/copy.wln
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/datascii.wln
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/formatter.wln
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/imagecrop.wln
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/matrix.wln
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/placement-joy\
 
>    stick.wln
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/placement-sli\
 
>    der.wln
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/placement.wln
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/record.wln
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/showopts.wln
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/specialchars.\
 
>    wln
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/textformat.wln
>> Snippets >> Loading >> /opt/WLJS\
 
>    Notebook/resources/app/wljs_packages/wljs-snippets/library/upload.wln
>> HTTPHandler[KirillBelov`HTTPHandler`HTTPHandler`$12]
>> Snippets >> AI loading...
StringRiffle::list: List expected at position 1 in StringRiffle[ulStyles].
>> Found black boxes: 
>> {/opt/WLJS\
 
>     Notebook/resources/app/wljs_packages/wljs-export-html/DynamicsTools/Bla\
 
>     ckBoxes/AnimationMachine.wl, 
 
>    /opt/WLJS\
 
>     Notebook/resources/app/wljs_packages/wljs-export-html/DynamicsTools/Bla\
 
>     ckBoxes/PavlovMachine.wl, 
 
>    /opt/WLJS\
 
>     Notebook/resources/app/wljs_packages/wljs-export-html/DynamicsTools/Bla\
 
>     ckBoxes/StateMachine.wl, /opt/WLJS\
 
>     Notebook/resources/app/wljs_packages/wljs-export-html/DynamicsTools/Bla\
 
>     ckBoxes/WidgetStateMachine.wl}
>> BlackBox :: AnimationMachine
>> BlackBox :: PavlovMachine
>> BlackBox :: StateMachine
>> BlackBox :: WidgetStateMachine
hash >> allocate 61698960 with offset 0
hash >> 342
hash >> ok!
opened on socket 0
LISTEN uintptr_t at 0
server: 0
creating async task...
Staring WS/HTTP server...
Hee uvTask: 1
Event-Loop started! 
hash >> allocate 61503840 with offset 0
hash >> 583
hash >> ok!
opened on socket 1
LISTEN uintptr_t at 1
server: 1
>> Downloads module was attached
>> Notifications >> Created spinner notifications type
>> Notifications >> Created custom notifications type
Protocol Loaded!
Settings Loaded!
Window Loaded!
Prompt window Loaded!
App Loaded!
Autolaunch!
>> >> Starting local LTP server ...
>> LocalKernel >> Starting using path:\
 
>    "/home/victor/wolframengine/14/SystemFiles/Kernel/Binaries/Linux-x86-64/\
 
>    WolframKernel" -wstp
CoffeeLiqueur`Notebook`LocalKernel`Private`LocalKernelObject[CoffeeLiqueur`No\
 
>    tebook`LocalKernel`Private`LocalKernelObject`$60]
Done?
Iframe app Loaded!
App Loaded!
>> InputNamePacket[In[1]:= ]
>> ReturnPacket[0]
>> ReturnPacket[Null]
>> ReturnPacket[/opt/WLJS Notebook/resources/app]
>> ReturnPacket[/opt/WLJS Notebook/resources/app]
>> ReturnPacket[{/opt/WLJS Notebook/resources/app}]
>> ReturnPacket[{/opt/WLJS Notebook/resources/app, 
 
>     /opt/WLJS Notebook/resources/app/wl_packages}]
>> InputNamePacket[In[2]:= ]
Open http://127.0.0.1:20560 in your browser
New connection for 2
hash >> allocate 140254841408368 with offset 0
hash >> 124
hash >> ok!
uv start readingbroadcast NewClient state!
# Loading by path : 
/home/victor/Documentos/WLJS Notebooks
Load settings one more time
>> SHORT!
OptionValue::optnf: 
   Option name AppEvent not found in defaults for Component$32453.
Default router
New connection for 3
hash >> allocate 140254841438448 with offset 0
hash >> 282
hash >> ok!
uv start readingbroadcast NewClient state!
>> InputNamePacket[In[3]:= ]
>> InputNamePacket[In[4]:= ]
>> Demos >> nothing to do. Up to date
>> InputNamePacket[In[5]:= ]
>> InputNamePacket[In[6]:= ]
>> InputNamePacket[In[7]:= ]
>> InputNamePacket[In[8]:= ]
>> InputNamePacket[In[9]:= ]
>> InputNamePacket[In[10]:= ]
>> InputNamePacket[In[11]:= ]
>> InputNamePacket[In[12]:= ]
>> InputNamePacket[In[13]:= ]
>> InputNamePacket[In[14]:= ]
Hee uvTask: 1
>> InputNamePacket[In[15]:= ]
>> InputNamePacket[In[16]:= ]
>> InputNamePacket[In[17]:= ]
>> InputNamePacket[In[18]:= ]
>> OutputNamePacket[Out[18]= ]
>> ReturnTextPacket[{Interpretation, InterpretationBox}]
>> InputNamePacket[In[19]:= ]
>> ReturnPacket[Null]
>> Kernel output >> Print: Establishing LTP link... using 127.0.0.1:36800
>> Kernel output >> Print: >> sid >> 0
>> Kernel output >> Print: Establishing starting LTP server for backlink...\
    
   >   using 127.0.0.1:36808
>> LocalKernel >> local kernel link connected!
>> LocalKernel >> PID: 41433
>> SocketObject[e9705059-cfdd-4138-9c2a-32fce4691c0a]
>> Kernel output >> State: Connected
>> Created! Spinner
Init Kernel!!!
>> Kernel output >> Notifications`Spinner[Notifications`Spinner`$76]: Null
>> Loading into Kernel... wljs-interpreter/src/Definitions.wl
>> Loading into Kernel... wljs-editor/src/FrontendObject.wl
>> Loading into Kernel... wljs-editor/src/EditorKernel.wl
>> Loading into Kernel... wljs-editor/src/StandardForm.wl
>> Loading into Kernel... wljs-editor/src/Boxes.wl
>> Loading into Kernel... wljs-editor/src/BoxesWorkarounds.wl
>> Loading into Kernel... wljs-editor/src/OffloadExtension.wl
>> Loading into Kernel... wljs-editor/src/SetDirectoryKernel.wl
>> Loading into Kernel... wljs-editor/src/FrontSubmitKernel.wl
>> Loading into Kernel... wljs-editor/src/RemoteCellsKernel.wl
>> Loading into Kernel... wljs-editor/src/FrontendObjectMissingFetch.wl
>> Loading into Kernel... wljs-editor/src/StoreKernel.wl
>> Loading into Kernel... wljs-editor/src/NotificationsKernel.wl
>> Loading into Kernel... wljs-editor/src/MetaMarkersKernel.wl
>> Loading into Kernel... wljs-editor/src/AutocompleteKernel.wl
>> Loading into Kernel... wljs-editor/src/System.wl
>> Loading into Kernel... wljs-editor/src/RasterizeKernel.wl
>> Loading into Kernel... wljs-editor/src/FrontendRuntimeKernel.wl
>> Loading into Kernel... wljs-graphics3d-threejs/src/Kernel.wl
>> Loading into Kernel... wljs-plotly/src/Kernel.wl
>> Loading into Kernel... wljs-graphics-d3/src/Kernel.wl
>> Loading into Kernel... wljs-inputs/src/Kernel.wl
>> Loading into Kernel... wljs-sound/src/Kernel.wl
>> Loading into Kernel... wljs-revealjs/src/Kernel.wl
>> Loading into Kernel... wljs-neuralnet/Kernel.wl
>> Loading into Kernel... wljs-export-html/DynamicsTools/ESP.wl
>> Loading into Kernel... wljs-manipulate/Diff.wl
>> Loading into Kernel... wljs-manipulate/Kernel.wl
>> Loading into Kernel... wljs-print-redirect-fix/Kernel.wl
>> Loading into Kernel... wljs-video/src/Kernel.wl
>> Loading into Kernel... wljs-wxf-accelerator/Override.wl
>> Starting WS link
>> LocalKernel Init >> Normal
nothing to do...
nothing to do...
nothing to do...
Kernel init...
Kernel init...
Kernel init...
>> LocalKernel Init >> Normal
nothing to do...
Kernel init...
>> LocalKernel Init >> Normal
>> LocalKernel Init >> Normal
>> LocalKernel Init >> Normal
>> LocalKernel Init >> Normal
>> Kernel output >> Connected: Please wait until initialization is complete!
Ok!
>> ReturnPacket[Null]
Open http://127.0.0.1:20560 in your browser
Open http://127.0.0.1:20560 in your browser
New connection for 4
hash >> allocate 140254841438704 with offset 0
hash >> 440
hash >> ok!
uv start readingbroadcast NewClient state!
>> Downloader >> Get request
>> Downloader >> Get request
>> Downloader >> Get request
>> Downloader >> Get request
>> Downloader >> Get request
>> Downloader >> Get request
>> Downloader >> Get request
>> Downloader >> Get request
>> Downloader >> Get request
>> Downloader >> Get request
>> Downloader >> Get request
>> Downloader >> Get request
>> Kernel output >> State: Initialized
>> ReturnPacket[Null]
>> ReturnPacket[Null]
>> Kernel output >> Print: Init js Kernel (Local)
>> ReturnPacket[Null]
>> ReturnPacket[Null]
>> Kernel output >> Print: Init internal communication
>> ReturnPacket[Null]
>> ReturnPacket[Null]
>> Kernel output >> Print: Init normal Kernel (Local)
>> ReturnPacket[Null]
>> ReturnPacket[Null]
>> ReturnPacket[Null]
>> ReturnPacket[Null]
>> ReturnPacket[Null]
>> ReturnPacket[Null]
Open http://127.0.0.1:20560 in your browser
>> Kernel output >> State: Initialized
New connection for 5
hash >> allocate 140254841438960 with offset 0
hash >> 599
hash >> ok!
uv start readingbroadcast NewClient state!
>> Downloader >> Get request
Read error ECONNRESET
writeerror !
making 5 closed by the reading thread!
broadcast Closed state!
New connection for 5
hash >> allocate 140254841439216 with offset 0
hash >> 757
hash >> ok!
uv start readingbroadcast NewClient state!
>> CSocketObject[5] was Closed
>> Downloader >> Get request
writeerror !
making 3 closed by the reading thread!
broadcast Closed state!
>> ExtendedApp >> Destroy
>> Kernel list holder >> destroyed!
>> Kernel >> Item.wlx >> destroyed!S

To me, it looks related to LLink or this uvloop, since it fails in both cases to load LLink on the first try. It looks like sometimes it just fails to fetch something. I see there are potentially related issues (#265 , #361 and #406 ) so maybe there's something off. Is there any way to fix it form WJLS or is it a Wolfram problem? It looks like their repos are kinda abandoned.

Thanks!

[JerryI]

Hi @VictorSeven

It is true we had some issues in the past when we did not bundle libuv.so dynamic library. According to the log line "UV loaded" it is not the case.

The error in the beginning you see mentioning v8 is related to the fact that LibraryLink does not provide any reliable way to determine llink version used internally by Wolfram Engine. Guys from WRI randomly change it from version to version and now we have v6, v7 and v8. The way how WLJS deals with that is it loads the newest one (v8, approximately corresponding to WE 14.2) then if it fails it goes to the older builds of sockets library and so on. For your case it was v7.

Regarding the license issues, I had somewhat similar on Windows machines from time to time, which was cured by cutting of the internet connection on the startup or upgrading Wolfram Engine. We have no clue why and when it happens, you may find similar issues reported for Jupyter WL Kernel extensions.

I would doubt that it is related to any WLJS parts personally from my worst dev experience working with Wolfram Engine... (among from other countless bug we found)

Another reason could be if you have any "stray" frozen Wolfram Kernels running in the background, it might crash new ones, but sometimes not immediately but after certain actions (I guess wolframscript periodically checks if there is any extra running instances of wl and then decides to kill it).

Sometimes wolframscript works, but wljs does not, because they effectively use different envs: one from your home bash profile, another one uses a different one since wljs electron wrapper spawns it using some nodejs env parameters. This then may affect the way how wolframscript checks the license activation...

(sorry, it all sounds very foggy, but thats what we get as a "freeware" wolfram kernel)

[JerryI]

Other things: if it was an anti malware issue, it would place all *so dynamic libraries to a quarantine and wljs would never start again after that

[VictorSeven]

Thanks for your answer! Yes, I understand that the difficulty comes basically from the architecture of Wolfram Engine rather than your part :) Wolfram does not seem very interested to really help the community. Still, I suspect there's something going on from the WLJS part, as I never had this problem with the Jupyter extension or to use wolframscript directly. In fact, while WLJS was completely blocked, I could still use both Jupyter and wolframscript normally. WLJS was the only one where the Engine would complain and return "license errors". The other issues I linked also failed with license errors, but the cause was completely unrelated.

To be honest, I was completely unable to connect the engine with VSCode, due to the mismatch between those libraries v8 and v7. That's why I thought that maybe WLJS could have this problem too.

The main problem updating the Wolfram Kernel now is that the official Jupyter extension (and the VSCode one too) seem to be not maintained anymore and I'm afraid they might stop working for new versions of the Engine. So WLJS will be the better supported option soon, and it would be fantastic to understand the origin of these issues.

If I can run any test for you let me know and I'll try to gather more information to narrow this down! Thanks! :)

[JerryI]

To be honest, I was completely unable to connect the engine with VSCode, due to the mismatch between those libraries v8 and v7.

I think the official extension for VSCode uses built-in sockets library of WL (which is horrible). At least we don't install our sockets library globally, so v7,v8 should only be active when using engine with wljs.

WLJS was the only one where the Engine would complain and return "license errors". The other issues I linked also failed with license errors, but the cause was completely unrelated.

Hm. Then it could still be related to env differences, that vscode spawns wolframscript using some other way. But this has to be checked...

If I can run any test for you let me know and I'll try to gather more information to narrow this down! Thanks! :)

Thanks! If you even face this issue again, please, try:

• disconnect from the internet and rerun WLJS
• run wolframscript -activate in the your system terminal
• if nothing works, try to run wolframscript from the system terminal and call get on the sockets test:

wolframscript -f '/path-to-wljs/app/wl_packages/KirillBelov_CSockets/Test/Test.wls'