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Subject: | RE: CA question with two identical servers |
From: | Emmanuel Mayssat <[email protected]> |
To: | "Goff, Steven J" <[email protected]>, "[email protected]" <[email protected]> |
Date: | Fri, 26 Jul 2013 14:17:31 -0700 |
Interesting ... EPICS is used at boeing... Just curious, what are you working on?
Although I am not an expert on the CA protocol, I believe this is not possible because client-server are connected using the reliable TCP protocol. (UDP broadcast are first used by the client to find the PV on a server, but thereafter it is a TCP one-to-one connection) That being said, I can see 2 ways to do this which consists mostly in 'hacking' your network. Those 2 methods are fundamentally the same though: have exactly the same machine (same IP) and duplicate the TCP packets. 1/ You need a computer. Use it as a gateway, i.e. like in a 'man in the middle attack'. That's relatively easy with a dual-interface linux box. 2/ If you have access to a > $1K network switch, log into one of them, use port mirroring. That's a common feature. -- Emmanuel From: [email protected] To: [email protected] Subject: CA question with two identical servers Date: Fri, 26 Jul 2013 14:32:53 +0000 I would like to use one CA application or MEDM display that will connect to two identical servers running the same PVs. I would like both servers to receive the Channel Access ca_put at the same time. This might mean I have to modify EPICS code for each server to receive the data simultaneously.
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