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

Subject: Re: Force TCP/IP reconnect from Asyn/Streamdevice
From: Christoph Schroeder <christoph.schroeder@helmholtz-berlin.de>
To: Torsten Bögershausen <torsten.bogershausen@esss.se>, <tech-talk@aps.anl.gov>
Date: Tue, 23 May 2017 13:22:53 +0200


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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Replies:
RE: Force TCP/IP reconnect from Asyn/Streamdevice Mark Rivers
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

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