Experimental Physics and
Industrial Control System

Matej Sekoranja <[email protected]> · Sun, 2 Aug 2009 20:49:18 +0200

Hi,

I have 2 questions about CAJ, the native Java Channel Access client
implementation.

1)  It seems like it behaves differently on computers with multiple

network interfaces from the C implementation. On the C

implementation

by default the broadcast address of each the networks is used when

searching for PVs. On the CAJ implementation this does not seem to

be

the case.  It is not finding PVs on one of these networks with the
default configuration, in my case on the 10.20.1.x subnet.  However,
if I set the following in my configuration file then it does work:

gov.aps.jca.Context.auto_addr_list= false
gov.aps.jca.Context.addr_list= 10.20.1.255

Is this an intended difference in behavior from the C implementation,
and if so is it documented?

Until Java 1.6, there was no (clean) way to "introspect" network

interfaces to get broadcast address of all. Therefore, CAJ uses

255.255.255.255 (auto) or be configured manually.

Java 1.6 supports this, but I do not want drop support for Java 1.5.

(Well, in fact I do a small "hack": compile code as 1.5 compatible,

detect Java version and use appropriate code).

2) My second question relates to knowing how to create configuration
lines such as those above in the JCALibrary.properties file.

The documentation links in the CAJ User Manual here:
http://caj.cosylab.com/manual.html

Include this one labelled "JCA tutorial on configuration":

http://www.aps.anl.gov/bcda/jca/jca/2.1.2/tutorial.html

But that tutorial only lists configuration lines like these:

gov.aps.jca.jni.JNIContext.addr_list= toto.uses.this.ca.server
gov.aps.jca.jni.JNIContext.auto_addr_list= false

These are for the JNI (e.g. C) implementation, not for the native

Java

implementation.

See
http://jca.cosylab.com/apidocs/gov/aps/jca/JCALibrary.html#CHANNEL_ACCESS_JAVA

for native CAJ options.

However you can use "gov.aps.jca.Context." prefix to configure all CA

java implementations, but note that specific configuration (prefix)

overrides the general one.

There is another link on the CAJ User Manual Page which is labelled

as

"CAJ configuration properties":
http://www.cosylab.com/jca/apidocs/gov/aps/jca/JCALibrary.html#CHANNEL_
ACCESS_JAVA

Link about is the right one now. Fixed. Thanks.

Cheers,
Matej

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System