KEPWare Timeout Error when Connecting to Modbus Device

[PID4Life]

I’m attempting to configure KEPWare to poll a Modbus device via Modbus TCP/IP. However, everything I’ve tried results in an error being reported in KEPWare. Details of the setup are below:

Networking:
The server running KEPWare and the Modbus device are connected directly together with a single Ethernet cable. The Modbus device is at IP 192.168.1.120 with subnet 255.255.255.0. The server running KEPWare is at 192.168.1.115 with subnet 255.255.255.0.

KEPWare Config:
KEPWare is configured with the following “device settings” to reach the Modbus device:

General

Driver: Modbus TCP/IP Ethernet
ID: <192.168.1.120>.0
Data Collection: Enabled​

Scan Mode

Respect Client-Specified Scan Rate​

Timing

Connect Timeout (s): 3
Request Timeout (ms): 1000
Attempts Before Timeout: 3​

When KEPware attempts to poll the Modbus device, the following error is returned:

TCP/IP.Device01 | Device is not responding. | ID = ‘<192.168.1.120>.0’​

I initially figured it was a networking issue, but I’m able to ping the Modbus device from the server running KEPWare. Also, I was able to poll the Modbus device using a test Modbus poll client so I know the device is working. It must be something wrong with my KEPWare configuration but I can’t seem to figure out what.

 

[FreakinControls]

Try a Modbus Simulator

Because you’ve verified the device and responding to Modbus requests using some other Modbus client, I do believe the issue is most likely a KEPWare configuration mishap. It’s tough to narrow those things down. Sometimes to simplify things, I start with a Modbus simulator that I know works with KEPWare just fine. It’s not uncommon for one Modbus client to work with a Modbus client, but another to struggle due to some different default setting.

Download SimServe from www.scadamatic.com to simulate the Modbus device on the same machine as KEPWare is running. See if you can get that working. If you can, then try getting it installing SimServe on a different server and have KEPWare poll across a network. My guess is you’ll have no trouble getting KEPWare to work with SimServe when it’s on the same machine. But once you put it on a different machine, you may see the timeout errors again.

That would let us know the issue is still networking related. Maybe something is wrong in the KEPWare channel settings?

 

[PID4Life]

Thanks so much for your help! The idea to try talking to a simulated Modbus device on the same server as KEPware got me thinking in the right direction.

Using a simulator on the same machine worked no problem, but the simulator on my laptop using the same Ethernet cable and IP address as the Modbus device resulted in timeout errors.

I looked again at the channel settings in KEPWare. I had KEPWare pointed at a network adapter that no longer existed (removed from virtual machine recently). After I fixed that, communications to simulator started without issue.

Then, I just replaced my laptop with the original Modbus device and it worked!

It’s always something small and dumb... Way too much time on that…