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<== Date ==> <== Thread ==>
Subject: Re: caget randomly returns Channel connect timed out
From: Matt Rippa via Tech-talk <[email protected]>
To: [email protected]
Cc: Talk EPICS Tech <[email protected]>
Date: Mon, 16 Jul 2018 09:39:02 -1000
Hi all,

Thanks for these replies. It is very possible we have newer Cisco switches installed
at various places throughout both our telescopes. I will try to find out the models and
see if we can capture packets on this one troublesome instrument (EPICS  3.14.8.2).

This thread has evolved. So I want to be clear that there may be two similar issues here:

1) In the original post I reported a problem how a script on linux calling caget once per
second can timeout talking to our new Telescope Control System (TCS) IOC running
RTEMS-4.10.2/EPICS-3.14.12.7. We couldn't find such timeouts on the legacy
TCS running VxWorks 5.4/ EPICS-3.13.9.   When these timeouts occur, we _DO NOT_
see any log messages on our TCS. I'll try to use Michael's cashark plugin to learn more.

2) Then, my colleague Ignacio at Gemini South posted a similar case where one of
our instruments (3.14.8.2) calls caget and often fails with the new TCS. Every time this caget
fails we see this:
Jul 12 12:40:59  E) PORT: tcs_vme, MSG: CAS: request from 172.17.102.130:57113 => bad resource ID                                                                 
Jul 12 12:40:59  E) PORT: tcs_vme, MSG: CAS: Request from 172.17.102.130:57113 => cmmd=12 cid=0xffffffff type=0 count=0 postsize=0 
Jul 12 12:40:59  E) PORT: tcs_vme, MSG: CAS: Request from 172.17.102.130:57113 =>   available=0x1       N=0 paddr=0x0 
Jul 12 12:40:59  E) PORT: tcs_vme, MSG: CAS: forcing disconnect from 172.17.102.130:57113 

There's a Holiday in Chile today but I hope they can arrange to capture some packets
in the next day or two. Details are forthcoming.

Thank you again,
-Matt


On Mon, Jul 16, 2018 at 8:59 AM Andrew Johnson <[email protected]> wrote:
Hi Mark,

On 07/16/2018 12:18 PM, Mark Rivers wrote:
> I thought we were doing directed UDP broadcasts to Cisco switches at
> the APS.
...
> Isn't that doing a directed UDP broadcast to the switch for the
> 164.54.162.* subnet?

If my internal investigations are correct you have an HP ProCurve switch
connecting your two subnets, which is why this still works for you.

Apparently it *is* possible to configure Cisco switches to allow this,
according to the last answer to this StackOverflow question:


https://stackoverflow.com/questions/379015/udp-broadcast-packets-across-subnets

This article from Cisco seems to explain how:
  http://www.ciscopress.com/articles/article.asp?p=330807&seqNum=9

If you have a system available with a network interface on both subnets
you could also run a pair of UDP Broadcast Packet Relays to pass
broadcasts between them, on both ports 5064 and 5065. More information
on this is available at

https://wiki-ext.aps.anl.gov/epics/index.php/How_to_Configure_Channel_Access#UDP_Broadcast_Packet_Relay

- Andrew

--
Arguing for surveillance because you have nothing to hide is no
different than making the claim, "I don't care about freedom of
speech because I have nothing to say." -- Edward Snowdon


--

References:
caget randomly returns Channel connect timed out Matt Rippa
Re: caget randomly returns Channel connect timed out Andrew Johnson
Re: caget randomly returns Channel connect timed out Michael Davidsaver
Re: caget randomly returns Channel connect timed out Matt Rippa
Re: caget randomly returns Channel connect timed out Dirk Zimoch via Tech-talk
Re: caget randomly returns Channel connect timed out Andrew Johnson
RE: caget randomly returns Channel connect timed out Mark Rivers
Re: caget randomly returns Channel connect timed out Andrew Johnson
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