[Jack-Devel] Port number limitation

Hannes Helmholz hannes.helmholz at chalmers.se
Fri Aug 23 13:36:13 CEST 2019



On 2019-08-21 22:52, John Rigg wrote:
> On Mon, Aug 19, 2019 at 08:54:04PM +0200, Hannes Helmholz wrote:
>> I have noticed the JACK server limitation of port numbers in some
>> specific applications ("Maximum number of output ports is reached for
>> application ref = 2"). I have noticed the "-p" / "--port-max" parameter
>> and was able to artificially scale down or up the available number. But,
>> I seem to have reached and upper limit at around 800. Due to possibly
>> already existing ports like system input and output I am not certain of
>> the exact number.
> 
> jack_lsp should show a list of all ports.
>  
>> To be fair, the available number is high enough for general use cases
>> (also for me). But in these certain conditions it definitely limits my
>> possibilities without an apparent workaround.
>>
>> Is there a way monitor if the port-max is passed correctly? Or where the
>> limitation arises otherwise? Or how to possibly circumvent it?
> 
> In jack2 (don't know about jack1) PORT_NUM_MAX is set in
> JackConstants.h. It's currently set to 4096.
> 
> There are other numbers in JackConstants.h like DRIVER_PORT_NUM
> (currently 256 which is too small for multiple MADI cards,
> for example).
> 
> If you can't get enough ports you might have to raise one or
> more of those numbers and recompile.
> 
> John
> _______________________________________________
> Jack-Devel mailing list
> Jack-Devel at lists.jackaudio.org
> http://lists.jackaudio.org/listinfo.cgi/jack-devel-jackaudio.org
> 

Ahh, thank you for the hint. The wall I was actually running into here
was PORT_NUM_FOR_CLIENT being 768.

What is the reasoning for these limits, since just like that they seem
very arbitrary? But at least there is a known source for the limitations
now. :)

Sadly recompiling is certainly not trivial, mostly because I need to
work with OSX and eventually Windows. Which both are not officially
supported atm, I believe.
In case I manage, should it be feasible to raise some of the limits? Or
what might happen that I will have to look out for?

/Hannes

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