Re: Question about PVaccess and docker

[Florian Feldbauer via Tech-talk <tech-talk at aps.anl.gov>]

Hi Giles,

thanks for the answer!

Best regards,
Florian

On 9/11/24 15:26, Knap, Giles (DLSLtd,RAL,LSCI) wrote:

Hi Florian,

I have seen exactly this issue and it is discussed in some detail here https://github.com/epics-base/pvAccessCPP/issues/197.

Regards,

giles

---

From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Florian Feldbauer via Tech-talk <tech-talk at aps.anl.gov>
Sent: 11 September 2024 14:17
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Question about PVaccess and docker

 

Hey all,

we use docker to manage and distribute our IOCs.

Assume the following:

I have two PCs connected via LAN.
On PC A I ran a docker container containing an IOC
ON PC B I try to access PVs of this IOC via caget/pvget (locally installed).

If I start my docker container with the `--network host` option (the
container uses the network of PC A), both caget and pvget are working fine.

But if I use the Docker's default bridge network and map the ports of
the container to the ports on PC A (`-p 5064:5064 -p 5064:5064/udp -p
5075:5075 -p 5076:5076/udp`) only caget works.
The ioc does not reply to any request on port 5076/udp
I also tried to use pvlist which returns nothing. But `pvlist <IP of PC
A>` works.

I used wireshark to check. The only difference in these two scenarios I
can see are broadcast messages send regularly by the ioc to ports
5065/udp and 5076/udp.
This difference is to be expected, as network bridges do not forward
broadcasts, so these are only visible in the 1st case.

Any idea why pvget/pvlist cannot connect with my ioc if I use the `-p`
options when starting the docker container?

Best regards,
Florian

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Dr. Florian Feldbauer
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Ruhr-Universität Bochum
AG der Experimentalphysik I
Dr. Florian Feldbauer
NB 2/131 / Fach 125
Universitätsstr. 150
D-44801 Bochum

Office: NB 2/134
Phone:  (+49)234 / 32-23563
Fax:    (+49)234 / 32-14170
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