directory-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Bharath Sundararaman" <Bharath.Sundarara...@starthis.com>
Subject RE: [MINA] and readiness selection
Date Mon, 25 Jul 2005 15:50:38 GMT
Hi Niclas,

Do you have any example code where MINA sends/receives data from a PLC?
I'm trying to use Ethernet/IP (CIP over Ethernet) to talk to PLCs in
vain.

Bharath.

-----Original Message-----
From: Niclas Hedhman [mailto:niclas@hedhman.org] 
Sent: Wednesday, July 20, 2005 1:55 AM
To: Apache Directory Developers List
Subject: Re: [MINA] and readiness selection

On Wednesday 20 July 2005 02:34, Bharath Sundararaman wrote:
> Scenario 2
> I have an application that does asynchronous reads and writes to
devices
> (e.g. PLC) via ethernet/ip. 

> So, communication with the device happens using a SelectableChannel
(tied
> to the device's IP address) which registers with a selector for
read/write
> interest and when data has to be read from a device, a read event is
pushed
> onto a queue, selector is woken up and read happens. There could be
many
> reads happening at the same time or alternate reads and writes in a
totally
> ad-hoc fashion. Is MINA a good choice for this scenario where you send
and
> receive bytes of data to devices?

I don't think this is any more unique to MINA than for normal sockets.
You 
would always need to provide the scheduler of request/response pairs,
and the 
algorithm of how much concurrency can occur over the same port, which is

probably defined by the devices. My guess is that most PLCs will only
allow 
one request for connection, which also makes the scheduler on the
"client" 
simpler.

For real high perfomance communication subsystems to PLCs, it is likely
that 
you will need a 3 stage SEDA architecture, where the you have an Encode,

Communicate and Decode stage independently chewing away at their
respective 
parts. And in that fashion, it seems to me MINA fits the bill well.


If PLCs are "your daily bread", then I would like to advertise a just
started 
project of OpenHMI.org, which will look into developing the HMI side of
the 
equation. This effort is not yet started, mainly awaiting the holiday
seasons 
in Sweden to finish.

Cheers
Niclas

Mime
View raw message