Experimental Physics and
Industrial Control System

Ralph Lange <[email protected]> · Tue, 25 Feb 2014 13:33:07 +0100

On 25.02.2014 13:22, David Michel wrote:

Hi All,

I have a device with an IP (i.e. a computer on the network which then

talks to other devices, but we'd like to treat it as a black box) and

I'd like to be able to do a "pulse check" from an IOC running on

another machine to detect whether it's still running or not.

Just as a quick test, I wrote a quick C function that performs a

'ping' and hooked that up to an aSub record. That works fine but, as

you can imagine, it's obviously very slow and keeps the device busy

responding to ping calls all the time, so it's not very practical at

all.... there must be a better way!

Now, EPICS itself does this pulsecheck somehow as can be observed when

shutting down an IOC where others IOCs that depend on it will rather

quickly notify of this connection loss on the iocshell, or with OPIs

screens suddenly showing widgets as disconnected.

Wondering how this is done and how I can apply it to my case. Any

ideas most welcome.

All IOCs are sending UDP broadcasts (alive beacons) every 15 seconds

(default, configurable).

A client that sees an irregularity (beacon not arriving within 2x the

regular interval) pings the IOC on the existing TCP connection.

If the IOC does not respond with 5 seconds, the connection (and all its

channels) are marked as disconnected, client callbacks being executed.

Don't know how could apply to your setup, though.

Cheers,
~Ralph

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System