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From Sebastian Rühl <>
Subject Re: Subscriber emulation
Date Wed, 12 Sep 2018 13:30:52 GMT

I agree with Julian here; we could implement these things in a plc4j-util module or something
like that (or pooling in a plc4j-pool).

Regarding implementing a plcSubscriber based on PlcReader: I think I did that in the camel
component when no plcSubscriber is available if I remember correctly.
I would vote against implementing such thing in the core module as PlcSubscriber shall only
be used for „real“ notifications and not polled reads.


> Am 12.09.2018 um 13:33 schrieb Julian Feinauer <>:
> Hi Andrey,
> we use this heavily (as we want frequent updates from S7 plcs) and have built a complete
layer on top of the communication in the last year.
> So I strongly suggest to add this to the project but as another level.
> I think we can also provide some code for this feature.
> The main reason why this should be "standalone" from my perspective is that it has to
deal with things like ThreadPools or Executors and handling of connection losses and all those
> And questions on how to deal with timeouts (if the plc is pretty busy) and things like
> Patterns like circuit breaker or request collapsing can be useful if you poll enough
messages (or are even necessary).
> So in-depth we spent a lot of time with these things and do not see how we could make
a simple and easy to use solution for the core.
> Best
> Julian
> Am 12.09.18, 13:04 schrieb "Andrey Skorikov" <>:
>    Hello all,
>    since not all protocols and devices support the subscriber model, I 
>    believe that it is sensible to emulate the PlcSubscriber based on a 
>    PlcReader as a fallback. This could be realized by polling the device at 
>    a fixed rate in the client process. However, I am not sure whether this 
>    should be part of the core plc4j component, or implemented separately on 
>    top of it. What do you think?
>    Regards,
>    Andrey Skorikov

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