Experimental Physics and
Industrial Control System

Anze Zagar <[email protected]> · Fri, 24 Sep 2010 13:01:36 +0200

Hi Matthew,

Actually the issue is not on client side. CArepeater is used for client
applications to share the beacon UDP port (e.g. EDM screens and also
IOCs because they can be clients to one another...). We are wondering
here, how to host multiple soft IOCs on the same computer, possibly
sharing the same UDP CA request port. For broadcast UDP packets this is
not really an issue, because Linux UDP stack is implemented in such a
way that it by default fans out the packet to all services running on
that particular port. Though, I'm not convinced that this is really
standard UDP stack behavior and that we have any guaranties it will
still work with future versions of Linux kernel. The second problem is
that at some stage ITER may also want to configure some client to send
unicast requests. Then it will for certain not work on Linux because in
that case only one IOC will in fact receive the request.

I see a few possibilities here:
o) Ignore the problem and assume that in ITER broadcast UDP will always
be used and there will be no problems in future. This is also ok if we
assume that at some stage they will switch to EPICS v4 where port
sharing will no longer be an issue.
o) Do something with modular epics and have only one IOC application
running, hosting all the required IOCs as modules.
o) Assign different ports to different IOCs. This will very likely
course cause a lot of other manageability issues.

Cheers,
Anze Zagar.

On Fri, 2010-09-24 at 11:22 +0100, [email protected] wrote:
> Here at ITER, t 
> Hi Pam,
>  
> We use the CArepeater UDP server on our linux hosts. 
>  
> http://www.slac.stanford.edu/comp/unix/package/rtems/epics-3.14.6/base/html/CAref.html#Repeater
>  
> Is that what you need?
>  
> Cheers,
> Matthew
> 
>         
>         ______________________________________________________________
>         From: [email protected]
>         [mailto:[email protected]] On Behalf Of Pam Gurd
>         Sent: 24 September 2010 09:18
>         To: EPICS tech-talk
>         Subject: Soft IOCs and Port Numbers
>         
>         
>         
>         hey're asking me about how to manage the problem of ensuring
>         that each of the soft IOCs running on a host has a distinct
>         port number. 
>         
>          
>         
>         What have people done to solve this problem?
>         
>          
>         
>         Thanks.
>         
>          
>         
>            Pam.
>         
>         
> 
> 
> 
>  
> 
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System