Experimental Physics and
Industrial Control System

"J. Lewis Muir" <[email protected]> · Wed, 11 Feb 2015 11:43:10 -0600

On 2/11/15 8:06 AM, Kasemir, Kay wrote:
> The situation is different when the host is not connected to a real
> network, so all you have is "localhost" and no broadcast address.

For running locally, I just use the IPv4 address of the loopback
interface (127.0.0.1 in my case) by setting the following environment
variables (shown for a Bourne shell):

===
$ export EPICS_CA_AUTO_ADDR_LIST=NO
$ export EPICS_CA_ADDR_LIST=127.0.0.1
$ export EPICS_CAS_INTF_ADDR_LIST=127.0.0.1
$ export EPICS_CAS_BEACON_ADDR_LIST=127.0.0.1
===

This works for me.

(I actually also set EPICS_CA_REPEATER_INTF_ADDR_LIST=127.0.0.1, but
this is *not* part of EPICS Base; I patched my EPICS Base to use it
so that caRepeater would bind to the interface I wanted--the loopback
interface in this case.)

> As Ralph mentions, sometimes it works and sometimes it doesn't.

This could be due to the fact that broadcast support on the loopback
network seems to vary by platform.  For example, on OS X Yosemite
(10.10.2), broadcast on the loopback interface does not seem to work,
but on Ubuntu 12.04.5 LTS (3.13 kernel) it does.

Here's the test I used:

1. In two separate terminals run the following:

   $ nc -u -l 1234

2. In a third terminal run the following:

   $ echo TEST | socat - udp-datagram:127.255.255.255:1234,broadcast

On OS X Yosemite, nothing gets printed to the first two terminals, but
on Ubuntu 12.04.5 LTS, the first two terminals print "TEST".

> In addition, there seems to be some remaining difference between the
> C implementation of the channel access client library and the pure
> Java CAJ implementation.

What are these?  I would love to get them straightened out if possible!

Regards,

Lewis

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System