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<== Date ==> <== Thread ==>

Subject: Questions regarding CA protocol specification and phylosophy
From: Diego Sanz <dshernan80@gmail.com>
To: EPICS Tech Talk <tech-talk@aps.anl.gov>
Date: Wed, 13 Sep 2017 15:52:43 +0200
Dear EPICS community, I would like to ask you a set of questions related with the same topic, but for not creating different topic threads, I think that all of them can be treated in this one.

Following CA theory on http://www.aps.anl.gov/epics/docs/CAproto.html and trying to understand how data packages flow between IOCs and EPICS clients, I have the following questions.

Glossary: CA-1: port 5064; CA-2: port 5065


1. Theoretically, I can run 2 or more IOCs in the same host for the same IP. The first IOC takes CA-1-TCP for PV values data transmission with the clients, and the second one must take another port (e.j., 33003) so 33003-TCP for the same purpose. Besides both IOCs will be listening on the same UDP port CA-1. Now I lunch a #caget PVname where the EPICS_CA_ADDR_LIST is the same IP, and it works for one of the IOCs and not for the other. I do the same with CSS, and occurs the same... only one of the IOC PVs are reachable. Is there any other configuration regarding this issue?

2. CA theory says that the repeater process shall manage the communication between IOCs and clients (due to the problem of only one process can listen by one port on the same host). I suppose that when I run camonitor o caget, the caRepeater (that listen by CA-2 UDP port)  is in charge of that. Besides, every IOC sends a Beacon message to say to the repeater that it is alive. But, all the EPICS clients shall work in that way? If I kill caRepeter, and I launch the CSS, there is no process on the system listening by CA-2 UDP... this is normal? where is the repeater standalon process working? 

Thank you very much in advance

Diego



Replies:
Re: Questions regarding CA protocol specification and phylosophy Kasemir, Kay
Re: Questions regarding CA protocol specification and phylosophy Michael Davidsaver

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