Modbus Ethernet Stopped Communicating

[MEWART]

Running an application with 30 MODBUS Ethernet RTUs. App ran fine for days, then yesterday just stopped talking to the RTUs. Checked the obvious (network connectivity, went through reboot, made sure windows firewall is off, etc) but no luck. Can ping each RTU from the server, but Lookout 6.1 has comm failure. PC has two NIC cards (One on routable subnet, and second on RTU subnet). Looked at metric to be sure no problems there, but can't figure out the problem. Any help is appreciated

[Ryan.S]

Option->Modbus Ethernet Option. Enable the diagnostic file, input a path such as d:\, check "value in HEX". The Mdobus communication will be logged to the file. Attach the file here or upload to ftp://ftp.ni.com/incoming

Do all Modbus objects stop working?

[Ryan.S]

Please first install the 6.1 updates. It fixes a Modbus bug.

http://joule.ni.com/nidu/cds/view/p/id/904/lang/en

[MEWART]

Installed the updates, but still have same problem. MODBUS diags show socket timeout (HEX 0x2733).

[MEWART]

File uploaded to NI site (PrimeSite1.log). All MODBUS communications have stopped and give the same error in the debug mode.

[Ryan.S]

The error "open socket: xxxx" means the ethernet connection cannot be created. When the ip address in incorrect, or the networking has problem, you may got this error.

The error is not in Modbus communication, it is just network connection failure. So I first suggest you to "ping" the remote device in command line.

Go to Start->Run, input cmd. Input command

ping xx.xx.xx.xx

to test if the remote device can be ping by ip.

[MEWART]

I can ping each RTU from the server machine. Also I can run the RTU config utility (IP based) and can access the RTU(s) with out any problems. This is very strange.

[Ryan.S]

Create a new process, and add a Modbus object from the beginning. Let's see if it works. If it works, the problem is in the lookout process.

[MEWART]

Built a new process, one MODBUS object monitoring one input. Had RTU wired directly to PC (via crossover cable). Could ping RTU, but had comm failure. Looking closely at windows.

[Ryan.S]

Here is a Modbus master utility. Please use it to test the modbus connection.

Run the ModScan32. Connection->Connect, select Remove TCP/IP Server. Choose the register type, such as holding register. Let's see if the Modscan is able to connect your modbus devices.