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<== Date ==> <== Thread ==>

Subject: RE: Force TCP/IP reconnect from Asyn/Streamdevice
From: Mark Rivers <rivers@cars.uchicago.edu>
To: 'Christoph Schroeder' <christoph.schroeder@helmholtz-berlin.de>, Torsten Bögershausen <torsten.bogershausen@esss.se>, "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>
Date: Fri, 2 Jun 2017 20:42:42 +0000
Hi Christoph,

In thinking about a similar question today I realized that there may be a simpler solution for your problem.  You may be able to just use the asynOption disconnectOnReadTimeout to force the connection to reset on a read timeout.  This assumes you are reading the device with a timeout longer than you expect the time between periodic messages from the device.  Look at the drvAsynIPPort documentation (http://www.aps.anl.gov/epics/modules/soft/asyn/R4-31/asynDriver.html#drvAsynIPPort) for details.

Mark

-----Original Message-----
From: Christoph Schroeder [mailto:christoph.schroeder@helmholtz-berlin.de] 
Sent: Wednesday, May 24, 2017 3:53 AM
To: Mark Rivers; Torsten Bögershausen; tech-talk@aps.anl.gov
Subject: Re: Force TCP/IP reconnect from Asyn/Streamdevice

Hi Mark,

that actually worked. I am using 3 records, one counter that is
processed each time data is received, a record to save the old counter
value and a calc that compares both values which is processed every
other second. I monitored the calc and it shows me that the connection
was reset 2 times since yesterday. The device is working fine right now,
thanks a lot!

Best regards,
Christoph


On 05/23/2017 01:50 PM, Mark Rivers wrote:
> If you load an asyn record on this asyn port then you can use the CNCT (connect) field to force drvAsynIPPort to disconnect and reconnect the device.  This should be equivalent to restarting the IOC.  Have you tried this?  If it works then you just need to figure out some logic to tell when the device is hung up and write to this field twice, first with Disconnect and then with Connect.  Detecting when it has hung could be done with a longin record that increments each time you receive a message and then a calc record that processes periodically and checks to see if the longin record has stopped incrementing.
>
> Mark
>
> ________________________________________
> From: tech-talk-bounces@aps.anl.gov [tech-talk-bounces@aps.anl.gov] on behalf of Christoph Schroeder [christoph.schroeder@helmholtz-berlin.de]
> Sent: Tuesday, May 23, 2017 6:22 AM
> To: Torsten Bögershausen; tech-talk@aps.anl.gov
> Subject: Re: Force TCP/IP reconnect from Asyn/Streamdevice
>
> On 05/23/2017 12:26 PM, Torsten Bögershausen wrote:
>>
>> On 23/05/17 12:19, Christoph Schroeder wrote:
>>> Hello,
>>>
>>>
>>> On 05/23/2017 11:40 AM, Torsten Bögershausen wrote:
>>>>
>>>> On 23/05/17 10:53, Christoph Schroeder wrote:
>>>>> Hi Torsten,
>>>>>
>>>>>
>>>>> On 05/23/2017 10:40 AM, Torsten Bögershausen wrote:
>>>>>> Which side does the retransmission ?
>>>>>> The IOC ?
>>>>>> The device ?
>>>>> The device retransmits a package that the IOC already received
>>>>> again and
>>>>> again until it gives up. The IOC sends duplicate ACK. It seems the
>>>>> acknowledge is ignored on the devices side.
>>>>>> Now, well, it looks as if the reset was not processed by the IOC ?
>>>>>> At least it didn't cause the TCP connection to be terminated, right ?
>>>>> Right, netstat tells me the connection is still established, but there
>>>>> is no flow of data anymore and the buffers are empty. The last
>>>>> package I
>>>>> reveived from the device is the TCP RST.
>>>>>> Which OS are you using ?
>>>>>> Which version of asyn ?
>>>>>>
>>>>> My tests where done with Debian 7 and Debian 8. The asyn version is
>>>>> R4-30. The problem seems to be caused by a lower layer. I got the same
>>>>> problem with a simple TCP client I wrote and even with netcat, so Asyn
>>>>> isn't at fault here.
>>>>
>>>> You should be able to use the CONNECT_PER_TRANSACTION feature from asyn
>>>> by using
>>>> drvAsynIPPortConfigure("xx", "<host>:<port>[:localPort] http",0,0,0)
>>>>
>>>> (But I wonder if this helps, when your device seems to have such
>>>> problems)
>>> Thanks I will try this.
>>>
>>>> Another question:
>>>>
>>>> Is the IOC sending anything more to the device?
>>>> And wait the response ?
>>>> Why is it so quite on the line ?
>>>> When the IOC polls the device, there should be some traffic coming out,
>>>> I think.
>>>> If there is nothing to be polled from the IOC, then it doesn't matter,
>>>> if the underlying TCP connection is not working, half-broken or
>>>> whatever.
>>> The instrument sends unsolicited data starting directly after the
>>> connections is established. There is no active communication from the
>>> IOC to the device.
>> That is sad to here, because then the "http" trick doesn't help us:
>> The IOC will not send anything to the device.
>> So there is no need to re-open the connection.
>>
>> Is there a chance to poll the device at all ?
>>
>>
>> And/or:
>> What does the device do, if you use your netcat test setup.
>> and the connection is closed ?
>> Will it accept a new one and behave better then on the old one ?
> No chance for polling, communication on this port is read only. The data
> is only send to the first client connected to the port. Closing the
> connection and opening it again resp. rebooting the IOC or restarting
> the client / netcat works fine until the error happens again. I observed
> that the time until the error occurs depends on the number of TCP
> packages send by the device which can be increased by configuring a
> higher scan rate on the device. I think it's some kind of buffer or
> counter overflow on the device which is reset with a new connection.
>
>
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>
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>
> Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren e.V.
>
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>
> Sitz Berlin, AG Charlottenburg, 89 HRB 5583
>
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> D-14109 Berlin
>
> http://www.helmholtz-berlin.de


________________________________

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH

Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren e.V.

Aufsichtsrat: Vorsitzender Dr. Karl Eugen Huthmacher, stv. Vorsitzende Dr. Jutta Koch-Unterseher
Geschäftsführung: Prof. Dr. Bernd Rech (kommissarisch), Thomas Frederking

Sitz Berlin, AG Charlottenburg, 89 HRB 5583

Postadresse:
Hahn-Meitner-Platz 1
D-14109 Berlin

http://www.helmholtz-berlin.de

Replies:
Re: Force TCP/IP reconnect from Asyn/Streamdevice Christoph Schroeder
References:
Force TCP/IP reconnect from Asyn/Streamdevice Christoph Schroeder
Re: Force TCP/IP reconnect from Asyn/Streamdevice Torsten Bögershausen
Re: Force TCP/IP reconnect from Asyn/Streamdevice Torsten Bögershausen
Re: Force TCP/IP reconnect from Asyn/Streamdevice Christoph Schroeder
Re: Force TCP/IP reconnect from Asyn/Streamdevice Torsten Bögershausen
Re: Force TCP/IP reconnect from Asyn/Streamdevice Christoph Schroeder
RE: Force TCP/IP reconnect from Asyn/Streamdevice Mark Rivers
Re: Force TCP/IP reconnect from Asyn/Streamdevice Christoph Schroeder

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