RE: EPICS_CA_ADDR_LIST and multiple instances of a SoftIOC on Windows

["Manoussakis, Adamandios via Tech-talk" <tech-talk at aps.anl.gov>]

If the epics clients use the broadcast address, wont that allow multiple IOCs to listen on the same host on windows?

 

Adam

 

From: Tech-talk <tech-talk-bounces at aps.anl.gov> On Behalf Of Andrew Johnson via Tech-talk
Sent: Wednesday, September 14, 2022 10:57 AM
To: tech-talk at aps.anl.gov
Subject: Re: [EXTERNAL] EPICS_CA_ADDR_LIST and multiple instances of a SoftIOC on Windows

 

Hi Carsten,

The port number reported by the cainfo program is the TCP port that the IOC is using for client connections, not the UDP port that it's listening on for CA searches, you can't take port numbers from cainfo and put them in EPICS_CA_ADDR_LIST. Unless you explicitly configure them otherwise IOCs always listen for CA name searches on port 5064, the TCP port it should connect to is passed to a client in the UDP search reply.

I don't really understand your original email, did you mean to set EPICS_CA_ADDR_LIST to my_computer.bessy.de instead?

The problem with using a single hostname like this

set EPICS_CA_ADDR_LIST=ca_gateway.bessy.de
set EPICS_CA_AUTO_ADDR_LIST=NO

or even this

set EPICS_CA_ADDR_LIST=my_computer.bessy.de
set EPICS_CA_AUTO_ADDR_LIST=NO

is that clients will send name searches as unicast UDP packets to that machine, but only one CA server/IOC running there will see them because the OS only delivers unicast UDP packets to one of the servers when several are listening on a single shared UDP port. If you use a broadcast address it sends broadcast UDP packets, which do get delivered to all listening servers on the shared port. When you run multiple IOCs on a host they all share the same UDP port and only one of them (and probably the last one started but that's actually OS-dependent) will see the unicast search packets that the above configuration will generate. This is a common problem that is described with solutions for Linux here, but I don't know that we have a fix for IOCs running on Windows.

- Andrew

On 9/14/22 8:46 AM, Carsten Winkler via Tech-talk wrote:

Hi, Freddie,

thanks for the tip. I disabled all firewalls, but fortunately I have the
same result as before.

Hi, Steven,

I also tried your hint with ports in EPICS_CA_ADDR_LIST. But that
couldn't solve the problem for me either.
All ports were selected automatically by the two SoftIOCs without any
special configuration.
Why do you think it "looks like a strange configuration"? I have only
two SoftIOCs on the same computer. So I can shut down one of them
without affecting the variables of the other one. Especially for motor
records this can be very helpful.

Any other idea how to solve the problem?

Cheers,
Carsten

Am 13.09.2022 um 16:08 schrieb Hartman, Steven:

On Sep 13, 2022, at 9:20 AM, Carsten Winkler via Tech-talk
<tech-talk at aps.anl.gov> wrote:

   Context: "Channel: "TestPV:ai1", Connecting to:
my_computer.bessy.de:62425 <http://my_computer.bessy.de:62425>,
Ignored: ca_gateway.bessy.de:62425 <http://ca_gateway.bessy.de:62425>"

Are you running on a non standard port (62425) intentionally?

If so . . .

set EPICS_CA_ADDR_LIST = ca_gateway.bessy.de:5064
<http://ca_gateway.bessy.de:5064> ca_gateway.bessy.de:52425
<http://ca_gateway.bessy.de:52425>
set EPICS_CA_AUTO_ADDR_LIST=NO

But this looks like a strange configuration.

--
Steven Hartman
hartmansm at ornl.gov

--
Carsten Winkler
Software Developer
BE-IA-AOT / AG ELIS
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Geschäftsführung: Prof. Dr. Bernd Rech, Thomas Frederking

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14109 Berlin
Deutschland

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