回复: How to capture messages generated by PyEpics?

["Li, Ji via Tech-talk" <tech-talk@aps.anl.gov>]

Yes, I used PV name (ca.pv) or the IP address of the workstation from which messages were generated (ip.addr) as the filter.

Just tried to capture in the same way on the workstation with Wireshark 2.6.20. Got the same result.

I noticed that in the received messages for both caget and caput, there were only commands "Version" 0x00, "Search" 0x06, "User" 0x14, "Host" 0x15 and "Create channel" 0x12, while I was expecting to see "Read" 0x03 and "Write" 0x04 separately.

Best,

-Ji Li

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发件人: Mark Rivers <rivers@cars.uchicago.edu>
发送时间: 2021年2月18日 22:17
收件人: Li, Ji <liji@bnl.gov>
抄送: tech-talk@aps.anl.gov <tech-talk@aps.anl.gov>
主题: Re: How to capture messages generated by PyEpics?

 

I don’t think the Wireshark version will matter. Have you put a filter on what Wireshark captures, or on what is selected to display?

Mark


Sent from my iPhone

On Feb 18, 2021, at 8:26 PM, Li, Ji <liji@bnl.gov> wrote:


Thanks Mark. I expect Wireshark to be install & play. The one I used is an old installation on an old server. Will find another one and try it out.

Best,

-Ji Li

________________________________
发件人: Mark Rivers <rivers@cars.uchicago.edu>
发送时间: 2021年2月18日 20:11
收件人: Li, Ji <liji@bnl.gov>
抄送: tech-talk@aps.anl.gov <tech-talk@aps.anl.gov>
主题: RE: How to capture messages generated by PyEpics?


Ø   When I get/set from PyEpics (tried both PV module and CA module), the program was able to successfully get the up-to-date value of the PV and set new value to it,

Ø  > but no messages showed up. Doesn't PyEpics communicate using CA protocol messages? Are there specific filter/configuration to be done in Wireshark to show these messages?



There is no difference in the CA network messages using caget and PyEpics.    They both use the same libca.so library from EPICS base.



You must have something configured wrong in Wireshark or something.



Mark





From: Tech-talk <tech-talk-bounces@aps.anl.gov> On Behalf Of Li, Ji via Tech-talk
Sent: Thursday, February 18, 2021 4:52 PM
To: tech-talk@aps.anl.gov
Subject: How to capture messages generated by PyEpics?



Hi,



I'm trying to capture CA messages targeting a specific PV on the IOC server with Wireshark (v1.12.1) and Michael Davidsaver's cashark plugin (ca.pv or ip.addr as the filter). Wireshark was able to capture messages generated by caget/caput commands ran from bash. When I get/set from PyEpics (tried both PV module and CA module), the program was able to successfully get the up-to-date value of the PV and set new value to it, but no messages showed up. Doesn't PyEpics communicate using CA protocol messages? Are there specific filter/configuration to be done in Wireshark to show these messages? Thanks.





-Ji Li