Re: Finding the server where a PV's IOC is located

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

Hi Ralph,

I only have a basic understanding of how the channel access protocol works, but my understanding is that the client just makes a socket connection to a port and then sends the channel access commands. 

I might be making some incorrect assumptions, but I think that if to get the host from your local machine's perspective you send some channel access commands to a local port, then to get the host from the gateway machine's perspective you can just make a socket connection to the right port on the gateway machine and send the same commands, without needing to ssh in the gateway machine. Do you know if this is how it works?

Alex

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From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Ralph Lange via Tech-talk <tech-talk at aps.anl.gov>
Sent: Wednesday, November 24, 2021 2:44:50 AM
To: EPICS Tech Talk <tech-talk at aps.anl.gov>
Subject: Re: Finding the server where a PV's IOC is located

 

On Tue, 23 Nov 2021 at 21:41, Sobhani, Bayan via Tech-talk <tech-talk at aps.anl.gov> wrote:

If you type “cainfo <pv name>”, one of the fields it returns is “host”, which is often the server that the PV’s IOC is running on.

 

But sometimes the “host” is really a gateway server and not the IOC server itself. For example:

 

[...] 

And then to find the real IOC server I would do “ssh cagw01.cs.nsls2.local” and then do “cainfo XF:03ID-CT{RG:C2}T-I” again, and I get:

 

[...] 

And now I have xf03idc-ioc2-313.nsls2.bnl.local, which is the real IOC server. Is there a way to find this IOC server without ssh?

Using Channel Access? No.

Many installations (including NSLS 2 btw.) are using the ChannelFinder directory service to collect and provide that kind of information.

Cheers,
~Ralph