RE: Help in debugging ACF connection issue

[Stephen Dann - STFC UKRI via Tech-talk <tech-talk at aps.anl.gov>]

Hi Érico,

 

Try “After=network-online.target” and “Wants=network-online.target” instead. That’s what I’ve used in the past. “After=network.target” doesn’t do much, according to the docs (man systemd.special).

 

Regards,

Stephen

 

From: Tech-talk <tech-talk-bounces at aps.anl.gov> On Behalf Of Érico Nogueira Rolim via Tech-talk
Sent: 09 March 2026 14:54
To: Hu, Yong <yhu at bnl.gov>
Cc: EPICS Tech Talk <tech-talk at aps.anl.gov>
Subject: Re: Help in debugging ACF connection issue

 

Hi Yong!

 

Thank you very much for the thorough investigation of our issue, and even managing to reproduce it! I greatly appreciate it.

 

We are indeed using systemd, so I will try to use the After=network.target directive first. I hope to be able to test this tomorrow, so I will let you know about the results then.

 

Cheers,

Érico

 

PS: I noticed that the systemd-softioc repository has been archived. Are you using something else now?

 

On 3/6/26 20:02, Hu, Yong wrote:

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Hi Michael,

 

I did the whole test again after adding a CA link to "myCommand:just4TestACF" in my first softIOC. Both dbCa and asCa cannot connect if my network is turned off at the beginning. 

 

You mentioned that EPICS_CA_AUTO_ADDR_LIST (and EPICS_CA_ADDR_LIST) is evaluated once at startup. That is a very point. So, I did one more test by setting EPICS_CA_ADDR_LIST to a broadcast IP, i.e. 192.168.12.255 (EPICS_CA_AUTO_ADDR_LIST seems Okay with either YES or NO)

$ softIoc -d test.db -a default.acf

asSetFilename: Warning - relative paths won't usually work

Starting iocInit

############################################################################

## EPICS R7.0.5

## Rev. 2021-05-13T07:10-0400

############################################################################

CAC: error = "Network is unreachable" sending UDP msg to 192.168.12.255:5064

Warning: RSRV has empty beacon address list

iocRun: All initialization complete

...

epics> epicsParamShow

EPICS_CA_ADDR_LIST: 192.168.12.255

EPICS_CA_CONN_TMO: 30.0

EPICS_CA_AUTO_ADDR_LIST: YES

 

 

Now, both dbCa and asCa automatically connect once my network is turned on.

epics> ascar

1 channels 0 not connected

 

epics> dbcar

CA links in all records

Total 4 CA links; 4 connected, 0 not connected.

    0 can't read, 0 can't write.  (0 disconnects, 0 writes prohibited)

 

epics> casr 1

Channel Access Server V4.13

1 client connected:

    TCP client at 192.168.12.44:61165 'wps-168932.lan':

      User 'yonghu', V4.13, Priority = 0, 1 Channel

CAS-TCP server on 0.0.0.0:5064 with

    CAS-UDP name server on 0.0.0.0:5064

Sending CAS-beacons to 0 addresses:

 

 

Érico, you have two ways to fix the ACF connection issue: add EPICS_CA_ADDR_LIST to your IOC's environment variable; OR make sure your network is ready before your IOCs start up.

 

Cheers,

Yong

 

From: Michael Davidsaver <mdavidsaver at gmail.com>
Date: Friday, March 6, 2026 at 4:51 PM

 

Hi Yong,

 

 

On 3/6/26 2:59 PM, Hu, Yong wrote:

...

3.  Manually start the first softIOC 'bpm-fron':  it has an ACF which reads a PV (myCommand:just4TestACF) that is provided by the second softIOC 'bpm-rear' .

Could you also add a record with a CA link to "myCommand:just4TestACF"?

I would be interested to know if you have a situation where dbCa can connect, but asCa can not.

also, with https ://github.com/mdavidsaver/cashark the "tshark" CLI can give more meaningful output than "tcpdump".

...

 

Conclusion: just as I mentioned below, most likely your IOCs start before your server's network is fully functional (valid IP address). 

 

To CA developers: Is this a feature or a bug in the Access security Channel Access (asCa)?

This may be related to the behavior of EPICS_CA_AUTO_ADDR_LIST=YES, which is evaluated once at startup using the list of interfaces configured at that time.

 

 

 

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