Argonne National Laboratory

Experimental Physics and
Industrial Control System

1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  2011  2012  <20132014  2015  2016  2017  2018  2019  Index 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  2011  2012  <20132014  2015  2016  2017  2018  2019 
<== Date ==> <== Thread ==>

Subject: Re: multiple servers on the same (loopback) interface
From: D Peter Siddons <siddons@bnl.gov>
To: tech-talk@aps.anl.gov
Date: Tue, 09 Jul 2013 15:08:59 -0400
I had a similar problem a couple of weeks ago. The fix for that was to add entries in the /etc/hosts file to provide the reverse lookup.
Pete.

On 07/09/2013 02:46 PM, Mark Rivers wrote:
This is probably the problem of DNS resolution timing out because there is no DNS server to do the reverse DNS lookup on that interface.

Mark


-----Original Message-----
From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Jameson Graef Rollins
Sent: Tuesday, July 09, 2013 1:42 PM
To: Kasemir, Kay; tech-talk@aps.anl.gov
Subject: Re: multiple servers on the same (loopback) interface

On Tue, Jul 09 2013, "Kasemir, Kay" <kasemirk@ornl.gov> wrote:
The first IOC will serve on TCP port 5065.
The second one can't do that, so you get the warning Configured TCP port was unavailable, ...Using dynamically assigned TCP port 34497.
Both will try to listen to UDP search requests on the same port, then reply with the TCP port that they actually use, so all should be fine.

BUT: Because of a quirk in most network kernels only one of them will actually see those UDP search requests. For me it's usually the IOC started _last_.

If you want your clients to send search requests to all IOCs that are listening on the UDP port, you need to send a broadcast. Search requests sent to a specific IP address will only reach one of the IOCs listening on that IP.

You can try setting the EPICS_CA_ADDR_LIST=255.255.255.255.
With localhost, that may not be possible, so you'll have to setup some network interface, maybe leave it disconnected, but it must have an IP address and most important a broadcast address.
Hi, Kay.  Thanks for the suggestion.  This is a possibility that I
considered, but since it requires administrative privileges to create
and configure the dummy interface it's less than ideal for a generic
testing infrastructure.

That said, I did give it a try and it does sort of work.  The dummy
interface is 127.2.0.1, and both servers bind to it.  However, the
client access is very slow:

0$ time EPICS_CA_ADDR_LIST=127.255.255.255 EPICS_CA_AUTO_ADDR_LIST=NO caget -t TEST0:FOO
0

real	0m6.292s
user	0m0.000s
sys	0m0.012s
0$

The initial response is fairly quick, but there's a long delay before
process returns.  Is using a broadcast address know to introduce a
noticeable delay like this?

jamie.



--
D. Peter Siddons
Detector Development Group Leader
Bldg. 535B
Photon Sciences Directorate,
Brookhaven National Laboratory
Upton, NY 11973

email: siddons@bnl.gov
Phone: (631) 344-2738


References:
multiple servers on the same (loopback) interface Jameson Graef Rollins
Re: multiple servers on the same (loopback) interface Kasemir, Kay
Re: multiple servers on the same (loopback) interface Jameson Graef Rollins
RE: multiple servers on the same (loopback) interface Mark Rivers

Navigate by Date:
Prev: RE: multiple servers on the same (loopback) interface Mark Rivers
Next: New version of STAR EPICS Virtual Machine (July 2013) Jiro Fujita
Index: 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  2011  2012  <20132014  2015  2016  2017  2018  2019 
Navigate by Thread:
Prev: RE: multiple servers on the same (loopback) interface Mark Rivers
Next: RE: multiple servers on the same (loopback) interface Hill, Jeff
Index: 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  2011  2012  <20132014  2015  2016  2017  2018  2019 
ANJ, 20 Apr 2015 Valid HTML 4.01! · Home · News · About · Base · Modules · Extensions · Distributions · Download ·
· Search · EPICS V4 · IRMIS · Talk · Bugs · Documents · Links · Licensing ·