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From Christofer Dutz <christofer.d...@c-ware.de>
Subject Re: Some of the latest changes
Date Mon, 01 Apr 2019 10:53:48 GMT
Yeah ... 

I guess we have to distinguish between 3 things:

1) The physical connection itself
2) The logical connection in the protocol
3) Testing if the logical connection is practically usable

I guess for 1) and 2) that's what we already have and what the "isConnected" in the NettyPlcDriver
does.
I agree, we need something for 3) .. but I wouldn't call the current solution "the best approach"
...

I'll try to whip up an alternate proposal in a feature branch ...

Got plenty of time anyway ;-)

Chris



Am 01.04.19, 12:29 schrieb "Julian Feinauer" <j.feinauer@pragmaticminds.de>:

    Hi Chris,
    
    Please keep in mind how this came to life.
    We always discussed a sensible and driver specific ping method, like in the S7 case do
a query against the slz or so.
    
    This is the best approach.
    
    The current approach works very inoptinal as observed in many applications from us and
also Gunter. Thus, I see this as a first step from not so good to a bit better.
    But ideally we implement something really good for each protocol.
    At least now we observe disconnects way faster as before which is important in many use
cases.
    
    Julian
    
    Von meinem Mobiltelefon gesendet
    
    
    -------- Ursprüngliche Nachricht --------
    Betreff: Re: Some of the latest changes
    Von: Christofer Dutz
    An: dev@plc4x.apache.org
    Cc:
    
    Another problem I am seeing is that there is a great difference between ping and isConnected.
    
    Ping simply checks if there is someone answering at the other side. While isConnected
also gives an answer to the current state of the protocol connection.
    
    So it is for example possible to still have a valid TCP connection but the protocol has
already said goodbye and therefore the connection is disconnected. Or which is much more likely,
the TCP connection has just been established, however the handshake has not yet been successful.
Especially with protocols like S7 and EthernetIp where the connection requires multiple interactions
with the remote and there is a goodbye in the protocol,
    This is important.
    
    Chris
    
    Am 01.04.19, 10:48 schrieb "Christofer Dutz" <christofer.dutz@c-ware.de>:
    
        Hi Matthias and all others,
    
        Well actually, prior to these changes, the AbstractPlcConnection didn't have any code
that was somehow related to the way communication is done. It sort of just provides the default
implementations for all of our APIs functions:
        - readRequestBuilder
        - writeRequestBuilder
        - subscribeRequestBuilder
        - unsubscribeRequestBuilder
        ...
        So implementations only need to implement the methods it actually supports and for
all others the default PlcUnsupportedOperationException throwing versions are used.
    
        Currently the part where the underlying connection-media comes in is in NettyPlcConection
but here it's still agnostic to the type of connection ... So both serial and ip based connections
use the same base-class.
        The type of connection is here passed in via the ChannelFactory where currently the
following flavors are available:
        - TcpSocketChannelFactory
        - SerialChannelFactory
        - RawSocketChannelFactory
        - UdpSocketChannelFactory (Doesn't exist but would need to implement this for KNX
protocol)
    
        So instead I would suggest to move the ping method into the ChannelFactory instead
and to implement the isConnected method in the NettyPlcConnection class, which then uses the
ChannelFactory's implementation to actually do the check.
    
        Chris
    
    
    
        Am 01.04.19, 10:31 schrieb "Strljic, Matthias Milan" <matthias.strljic@isw.uni-stuttgart.de>:
    
            Hi Chris,
    
            There I would throw in a counter-question, namely whether it would be important
at this level to distinguish between automation protocols and fieldbus systems as AbstracConnectors?
Because Profinet and EtherCat are protocols that differ a bit from the data handling of an
OPC UA, ADS or S7 and are also quite sensitive regarding the deterministic real-time (EtherCat
is a bit looser). Those types need a bit more configuration information like message structure,
pull rate and master node.
    
            Then, of course, it would have to be evaluated whether these two communication
systems should be separated and whether automation protocols exist on a basis other than TCP/UDP?
            Just take it as creative discussion point.
    
            Greetings
            Matthias Strljic, M.Sc.
    
            Universität Stuttgart
            Institut für Steuerungstechnik der Werkzeugmaschinen und Fertigungseinrichtungen
(ISW)
    
            Seidenstraße 36
            70174 Stuttgart
            GERMANY
    
            Tel: +49 711 685-84530
            Fax: +49 711 685-74530
    
            E-Mail: matthias.strljic@isw.uni-stuttgart.de
            Web: http://www.isw.uni-stuttgart.de
    
            -----Original Message-----
            From: Christofer Dutz <christofer.dutz@c-ware.de>
            Sent: Monday, April 1, 2019 10:06 AM
            To: dev@plc4x.apache.org
            Subject: Some of the latest changes
    
            Hi all,
    
            today I simply have a little time to inspect the latest changes as I was travelling
for 5 days ... I do have a few questions:
    
            Why is AbstractPlcConnection been extended by a getInetSocketAddress method?
    
            PlcConnections are not bound exclusively to TCP/UDP ... we currently already have
Serial port based connections and when going into protocols like Profinet and EtherCat in
the future we'll be going down to IP or even Ethernet level.
            I don't like TCP/UDP details in the base abstract class for all drivers.
    
            ... continuing to evaluate ...
    
            Chris
    
    
    
    
    

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