Experimental Physics and
Industrial Control System

Emmanuel Mayssat <[email protected]> · Mon, 01 Oct 2007 12:23:05 -0700

Hello all,

I currently have some client applications which do not reconnect to my
server once an IOC is restarted (after 24h of being shutdown).
I want to solve that issue.

My current understanding of the way CA clients is the following:
When a client is started, it attempts to fetch the PV according the
EPICS_CA_ADDR_LIST (default port if not explicit is
EPICS_CA_SERVER_PORT)

If the client still cannot find a PV, it sends another search requests
to all servers listed in EPICS_CA_ADDR_LIST. It continues doing at
increasing intervals. At one point it will stop sending search requests.

Q: Are search request TCP based?

At that point the only thing that can wake it up is a beacon anomaly.

Q: Who/what detects beacon anomalies? Is it the caRepeater?

Beacon are sent by IOC server as soon as they are started.
Beacon are UDP broadcasted by IOC server from EPICS_CA_SERVER_PORT to
EPICS_CA_REPEATER_PORT at the frequency given by
EPICS_CA_BEACON_PERIOD. 

Q: Where are the beacon sent? IP address? Port? transport protocol?

If caRepeater daemon was spawned on client, it receives the beacons,
detect a beacon anomaly and inform the registered clients that some new
PVs are available.

Q: Is it possible that the caRepeater is not spawn? (for ex if not in
client application path)

Q: What happens if you have several caRepeater processes running on
client? Do they maintain the same list of registered client processes?
On some of my machines, I have several caRepeater processes...

Q: How can I list all clients registered with a caRepeater?

Q: What if server and client do not have the same
EPICS_CA_REPEATER_PORT? The beacon should not be sent by the IOC server
to the right location of the repeater, is this correct?
( I think this is the problem I have) 

Q: Should the EPICS_CA_REPEATER_PORT be the same on all IOC servers and
OPI clients?

Q: If the client had initially connected but then the IOC server goes
down, is the procedure the same? When are state of health messages sent?

Thanks,
--
Emmanuel

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System