Experimental Physics and
Industrial Control System

"Jeff Hill" <[email protected]> · Tue, 5 Jan 2010 14:03:09 -0700

Hi Dirk,

> I wonder why you get any reply at all using 255.255.255.255? Is there
> any "magic" in the IOC server that allows IOCs to respond to
> 255.255.255.255 and that is not included in the portable CA server?

$ excas &
[1] 17231 
$ netstat -a | grep 5064
tcp        0      0 *:5064                      *:*
LISTEN
udp        0      0 *:5064                      *:*

When I run excas, which is (similar to the gateway) based on PCAS (the IOC
is based on rsrv), I see (using netstat -a) that excas appears to _not_ be
bound to any particular network interface. So one is led to the (perhaps
early) conclusion that this is a side effect of the way your CA Gateway has
configured its environment variables. 

One might try to overcome this behavior by binding the gateway's CA server
selectively (using the EPICS_CAS_INTF_ADDR_LIST environment) to
255.255.255.255, but that might not produce the desired CA gateway behavior.
Also, watch out for multiply defined PVs should the default unrestricted CAJ
BC address be circulated too far by your routers future reconfiguration (to
both the GW its proxied IOC).

Jeff
______________________________________________________
Jeffrey O. Hill           Email        [email protected]
LANL MS H820              Voice        505 665 1831
Los Alamos NM 87545 USA   FAX          505 665 5107

Message content: TSPA

> -----Original Message-----
> From: [email protected] [mailto:[email protected]]
> On Behalf Of Dirk Zimoch
> Sent: Tuesday, January 05, 2010 7:08 AM
> To: Mark Rivers
> Cc: [email protected]
> Subject: Re: CAJ or PV gateway problem?
> 
> Mark Rivers wrote:
> > Folks,
> >
> > We found a problem with CAJ and the PV gateway yesterday.  The problem
> is that CAJ "out of the box" (e.g. without changing any of the default
> properties) will connect fine to PVs on the local subnet if they are
> contained in a VME IOC or soft IOC.  But CAJ will not connect to PVs that
> are present in a PV gateway on the local subnet.
> >
> > We've figured out the problem, and it is easy to reproduce even with
> traditional CA from EPICS base.  The problem is that CAJ defaults to a
> broadcast address of 255.255.255.255 when searching for PVs.  VME IOCs and
> soft IOCs respond to such a broadcast, but the PV gateway does not.
> >
> 
> Hi Mark,
> 
> The EPICS default, according to the CA Reference Manual, is to use the
> broadcast addresses of all network interfaces. (If this makes sense or
> not is another issue -- imagine an IOC and a CA client on the same
> computer with two network interfaces => duplicate channels.)
> This behavior can be modified with the environment variables
> EPICS_CA_ADDR_LIST and EPICS_CA_AUTO_ADDR_LIST.
> 
> The CA gateway parses its command line parameters for server and client
> address and modifies the environment variables before starting the CA
> server part. Normally, one specifies the broadcast address of one
> network card as the server address. Thus, I would say the gateway is
> working correctly.
> 
> If CAJ uses an other default and/or does not look at the environment
> variables, CAJ does not conform to the CA Reference Manual. I dare to
> say it is buggy. (And don't tell me "Java cannot read the environment"
> -- all Java fans say "Java can everything" :-P )
> 
> I wonder why you get any reply at all using 255.255.255.255? Is there
> any "magic" in the IOC server that allows IOCs to respond to
> 255.255.255.255 and that is not included in the portable CA server?
> 
> Dirk

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System