Re: Connecting EDM screens to multiple soft IOCs on the same machine on a separate subnet.

[Alan Greer <ajg@observatorysciences.co.uk>]

Andrew, Kay,

Thank you for your help and explanations of what is happening.  I will look at the solutions you have given.

Kind regards, Alan

On 16 October 2013 16:23, Andrew Johnson <anj@aps.anl.gov> wrote:

Hi Alan,

On 10/16/2013 09:01 AM, Alan Greer wrote:

I have a headless server (serv01) running two soft IOCs (IOC-01 and IOC-02).
I have another machine on a separate subnet that runs the EDM GUI
applications for those IOCs.
caRepeater is running on serv01.

caRepeater is only used by CA clients running on the same machine, so that won't help this situation at all.

I hope I have explained this with enough detail, can anyone help me so
that the connections to IOC-01 are not lost(?) when running up IOC-02.

Kay's explanation of the problem is correct, but there are alternative solutions to running a CA gateway.

1. You could run a CA Nameserver in the GUI subnet which knows about the IOCs and responds to search requests; in this case you would *not* set the EPICS_CA_ADDR_LIST variables. This is almost equivalent to running a CA Gateway, but is slightly more robust in that if the Nameserver process dies it wouldn't kill any existing connections.

2. If you have access to a machine with a network interface on both subnets you could also try running a program on it called UDP Broadcast Packet Relay https://www.joachim-breitner.de/udp-broadcast-relay/ which forwards broadcast packets between subnets. You would probably have to run it twice, once on port 5064 and once on 5065; the first one will forward CA search requests between the subnets, and the second sends the CA beacons. If you do have success with this please let us know, we use it here at the APS for forwarding timing UDP packets but not for CA.

- Andrew
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