Network connection stopped working; receiving Error 56 and 66

[jtrout]

An application that has been running for years suddenly stopped receiving communications from a barcode reader.  We are running LabVIEW 2011.  The barcode reader is a Keyence SR-610 with a N-L1 Ethernet communications box.  To debug the problem, I used only the vis related to the barcode communications, which were Telnet Open and Telnet Read.  The error messages that I got were error 56, which occurs at TCP Open Connection in NI_InternetTK_Core_VIs, and 66, which occurs at TCP Read.  We used the Keyence configuration software from the control room where the LabVIEW PC is located, and we were able to receive barcode messages, which implies that the barcode reader is functioning properly, and the network switches, cabling, etc. are ok.  Any suggestions for tests to try would be appreciated!

[jtrout]

An application that has been running for years suddenly stopped receiving communications from a barcode reader.  We are running LabVIEW 2011.  The barcode reader is a Keyence SR-610 with a N-L1 Ethernet communications box.  To debug the problem, I used only the vis related to the barcode communications, which were Telnet Open and Telnet Read.  The error messages that I got were error 56, which occurs at TCP Open Connection in NI_InternetTK_Core_VIs, and 66, which occurs at TCP Read.  We used the Keyence configuration software from the control room where the LabVIEW PC is located, and we were able to receive barcode messages, which implies that the barcode reader is functioning properly, and the network switches, cabling, etc. are ok.  Any suggestions for tests to try would be appreciated!

[rolfk]

This would indicate some kind of network configuration error. Error 56 (timeout error) on TCP Open means that the function could not establish a connection with the desired network device. Possible reasons:

- The TCP Open function is called with an erroneous timeout of 0 or close to 0 ms.

- The IP address of the device changed.

- The network cable or network adapter is defective.

- The network routing changed so that the subnet the device is located on is not visible anymore from your computer.

- A firewall intercepts and disables the connection to the device.

- Last bat not least: The device is defective.

As the device seems to use telnet as basic protocol you can easily use a terminal application like Putty to try to test the connection. If that works you can discard any hardware errors and concentrate on something that blocks your LabVIEW app from accessing the network, such as a firewall rule that disables network access based on the process name. 

[jtrout]

The barcode reader IP address and cabling seem fine, because we can communicate with the reader in the same room connected to the same network switch (with a different computer running different software).  My first thought was a permission or firewall issue.  We still haven't ruled that out.  Right now, I think it may be a problem with the network card on the LabVIEW PC.  It may be an intermittent problem.  The LabVIEW program is not trying to re-open the connection if it fails.  I never could get it to connect, but last night, the operator said he restarted several times, and the system began receiving input from the barcode reader again.  It also turns out that they have been experiencing some other issues lately with the network connectivity.  The system mainly is doing video inspection, and it runs around the clock processing video and transferring data over the network.  It wouldn't be the first time we have had a hardware failure.

[jtrout]

The Ethernet connection from the LabVIEW application to the barcode reader started working again and has continued to work for about a week.  We haven't had access to work on the system since it is back online.  This result makes me think that the connection was timing out due to hardware that is dying.  The PC running the application is scheduled to be replaced.