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Old July 29th, 2021, 05:50 AM   #1

Finnbliss is offline
Join Date: Jul 2021
Location: Roskilde
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Book TCP Socket Communication with A-B's between Logix Controllers

Silly question:
I would like to know if anyone has done TCP Socket communication between Logix controllers?
I do know it works fine from any Control or Compact Logix controller to a high level programmed application residing in a computer.

Now, I would like to do the same between Logix controllers.
As an example between a ControlLogix and a CompactLogix.

There is a reason not to use Ethernet IP in this case.
Anyone that has done this before?
Pls feel free to comment.
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Old July 29th, 2021, 08:17 AM   #2
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Contr_Conn is offline
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Location: Ohio
Posts: 2,292
We used it to test Modbus AOIs that are Sockets based. One PLC was running Client, another Server.

But not using a native Ethernet/IP is like inventing a bicycle with square wheels - your sockets comms will be much slower, less reliable and use all processor resources to parse the data that is normally done in firmware
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Old August 2nd, 2021, 03:40 AM   #3

Finnbliss is offline
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Location: Roskilde
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Cool Problem solved...

Hi, got the problem solved as questioned by me.
I know very well the entertainment using squared wheels.
But this was a customer request.

They wanted to use the same standard as they use with Siemens S7.

Of course in the same way with Rockwell controllers. :P.

I made the socket communication working and built AOIs' for TCP read and write to protect the code from third party itchy fingers messing it up.

Did all this by using an 1756-EN3TR module for ControlLogix and communicated directly to the CompactLogix built in Ethernet port.

The code functions just fine without any noticeable delays.
I based it all on the code that exists in RA's knowledge base with an EWEB module and the app attached.

Took me two days to figure it all out.
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Old August 2nd, 2021, 10:15 AM   #4
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Jim3846 is offline
Join Date: Dec 2019
Location: Cincinnati OH
Posts: 213
I think the delays i ran into is "Where is the start and end of that message? If there all variable length messages, then your stuck processing the message byte at a time to decide start, type of message, content, end. So to speed it up just bring a big chuck of the messages at the read buffer and do the processing internal of "start, type of message, content, end".

That is my only suggestion.
Plus i thought RA does give an AOI of the interface.
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Old August 3rd, 2021, 08:53 AM   #5

Finnbliss is offline
Join Date: Jul 2021
Location: Roskilde
Posts: 3
Smile Jim3846

No need to execute messages byte by byte.
The write socket has a standard connection size of 472 bytes.
Large connection size is 3972 bytes.
Depends how we configure the MSG instruction.

If this is not enough, we can use multiple sockets.

Saw that RA have AOIs' but I prefer my own with extended fault handling etc. I'm kind of old fashioned and do know what I have built. Hehehe.

Anyway, this was a good lesson for all TCP socket communication, no matter what is on the other end of a controller from RA.
Like other controllers, bar code readers, printers etc..
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