Controllogix CIP with SCADA using Large Forward Open Connected Messaging

[Tapas Thakker 0]

Hello Guys,

I am very new to CIP messaging and in our project, we are trying to Controllogix to SCADA server using CIP messaging:

What I understand from the process right now is :

1. SCADA Opens a connection for Large forward Open ( Connection size set at 2500 bytes)

2. PLC responds and establishes a connection

3. SCADA send an MSP request to access tags from PLC

4. PLC responds to this request

The problem we are facing is the PLC doesn't send out a response of more than 240 bytes,

Have any of you guys have faced a similar issue or can help me with troubleshooting?

 

Thanks in advance

Attached screen captures from wire 

 

 

 

 

 

Edited 7 Jun 2021 by Tapas Thakker

[Mark- 17]

Post a capture file. Screen shots do not show the data size you are requesting.

[Tapas Thakker 0]

Thanks Mark,

I have attached a screen capture of the Connection Manager trying to establish a connection of 2500 bytes.

However, further investigations suggest the cap is not on the size as the comms again fell over for a request of 12 attributes which was around 210 bytes.

I guess there is a limitation on the number of Multiple service packet requests? Don't seem to find where the problem is.

 

Regards,

Tapas

 

Edited 7 Jun 2021 by Tapas Thakker

[Mark- 17]

A WireShark capture file, not a screen capture. Not the size request for the forward open. The actual data sizes in the read service request. Repeat the actual WireShark capture file from register session to unregister session.

> I guess there is a limitation on the number of Multiple service packet requests?

No.

 

[Tapas Thakker 0]

I have attached the Wireshark log I got, don't know how the driver is configured but trying to figure out where the issue is.

 

On 4/7/2020 at 9:28 PM, Mark- said:

Repeat the actual WireShark capture file from register session to unregister session

Don't know how to do it, but will try and get these logs if I can

 

Thanks a lot for your help

Edited 7 Jun 2021 by Tapas Thakker

[Mark- 17]

> The problem we are facing is the PLC doesn't send out a response of more than 240 bytes,

You are only requesting data for 11 reals. Ask for more tag data and I assume the device will reply with more data, up to the requested specified buffer size, in the large forward open request.

Edited 7 Apr 2020 by Mark-

[Tapas Thakker 0]

In attached logs, there are two requests one for 11 reals and one for 15 reals 

The response for both is only with 11 reals

Initially thought it was because of the data size limit, but that is not the case

[Mark- 17]

You are correct.

Two reads, both using the same CIP sequence count value (1).

The controller sees a duplicate read and responds with the same reply as the first message.

 

[Tapas Thakker 0]

Got that Mark,

Thanks a lot, will fix and try it

Will let you know the results

Regards,

Tapas

[Tapas Thakker 0]

Hello Mark,

The fix that you pointed worked well and now we are able to work with the Large forward open request

Thanks a lot for your help

 

Regards,

Tapas

[Mark- 17]

2 minutes ago, Tapas Thakker said:

Thanks a lot for your help

You are welcome.

[Tapas Thakker 0]

Hi Mark,

Thanks a lot for your help earlier, 

Now we are trying to establish two separate TCP connections, this is because we have two CPU's on the same Rack and an EN2T card

Is it possible to use port numbers other than 44818 to access data?

Tried port number 49152-65535 range to test but it failed, giving a connection failure.

Regards,

Tapas

Edited 22 Apr 2020 by Tapas Thakker

[Mark- 17]

You are welcome.

You can use other port number yes. Is the slot (controller) part of the connection path?

[Tapas Thakker 0]

Yes Mark, The Controller slot is a part of the request path when a CIP connection is getting established.

Have attached a log, 

The issue is, when there is a Large Forward Open connection established with a Controller (Slot), and the server tries to establish another Large Forward Open with another Controller (Slot) it gets a connection failure

 

That is the reason for trying to use different ports, but we are getting connection failure when trying to use port number 49152-65535

 

Regards,

Tapas

 

Edited 13 Nov 2020 by Tapas Thakker
delete files

[Mark- 17]

Are you using a different connection serial number?

 

[Tapas Thakker 0]

Ok, got you

I can see that the serial number is same for both requests, so we have to use different serial numbers to have a separate connection to different slots

Will try and implement that and see

Thanks a lot again,will let you know the results

 

Regards,

Tapas

 

[Mark- 17]

I do not know if that is the issue. I see the result "connection in use or duplicate forward open" and know I code so the connection serial number is unique across all connections.

Edited 22 Apr 2020 by Mark-

[Tapas Thakker 0]

Thanks a lot again, you are awesome

Regards

Tapas

Edited 23 Apr 2020 by Tapas Thakker

[Mark- 17]

You are welcome. Do you have the CIP specification to read?

[Tapas Thakker 0]

Yes Mark, I got a copy of CIP spec Volume 1 and Volume 3

[Mark- 17]

OK, I asked because the specification is where I find solutions to most returned error codes. Word search (and patience) is your friend.

[Tapas Thakker 0]

That's True Mark, should be referring to documents first, but practicing patience is a very very difficult task

Thanks a lot!!

Regards,

Tapas