NetBurner Community Forum

Posted: **Fri Jul 18, 2014 1:10 pm**

Hello all...my first post here, so please go easy on me!

I'm attempting to connect to an SBL2e module using a 1769-L33ERM Allen Bradley PLC using a Socket connection. During the OpenConnection message routine, I get an error 16#0000_0016. Looking through the Rockwell knowledge base, I have found the following information:

Problem: A Logix Open Sockets (TCP Client) is unable to connect to a 3rd party device (Slave). The Connect Message faults with Extended Error codes 16#0000_0046, 16#0000_0016, or 16#0000_0033.

Cause
The device reports WIN=0 and the 1756-EN2T module immediately closes the connection. Below is a sample of a Wireshark capture that illustrates this point.

This is done for security reasons:

Zero window is not allowed.
Enable/disable acceptance of the peer window being set to zero in the ACK of the SYN/ACK.
An attacker can use zero window to keep the node in persist time for a long time.
Solution
1756-EWEB module does not do this check. There is no workaround on the Rockwell Automation side with EN2xx modules. Customers must contact the 3rd party vendors to increase Window size.

Does anyone have any idea how to increase the Window size, as mentioned above? I'm on a bit of a time crunch, so any help as soon as possible would be greatly appreciated!

Thanks for the help,
Matt

Posted: **Fri Jul 18, 2014 3:08 pm**

One more thing...I don't *need* to run the NetBurner as a TCP Server if there's a better (easier) way to connect to it from the PLC. Possibly by using it at a TCP Client, or using UDP, etc? Any thoughts there?

Posted: **Fri Jul 18, 2014 8:56 pm**

If the PLC supports UDP, that would probably be easier to implement for you.

Posted: **Sat Jul 19, 2014 2:55 am**

I just tried UDP, and I seem to be getting a similar error (16#0000_0046 in the "ReadSocket" message, but still covered by the previous knowledge base article that I posted). I have emailed customer support at NetBurner, and they recommended I open up a support ticket to speak with the engineering team to see if they can determine if it's possible to change the "Window size" to be something other than 0. Unfortunately, I'm not sure how to get the serial number for my device, so I can't figure out how to register on their site!

Anyone have any experience with changing the window size?

Thanks again,
Matt

Posted: **Sat Jul 19, 2014 3:04 am**

You just need the serial number from the Dev Kit. It's the same serial number you would have entered when you installed the dev tools as well.

Posted: **Sat Jul 19, 2014 3:25 am**

Unfortunately, I don't have the Dev Kit with me (I'm traveling internationally for business), and have never installed the Dev Tools....I only have the NetBurner SBL2e module with me.

Posted: **Sun Jul 20, 2014 6:20 am**

Zero window is perfectly legal and normal TCP.

I realize this does not help you, but a zero window is part of the specification...
It is how TCP does flow control.

Posted: **Wed Jul 23, 2014 1:44 am**

For udp it can't be a window size issue, because a udp packet does not have a window size field. It only has:

source port number
destination port number
datagram size
checksum

Maybe something else is not configured correctly?

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