Debugging Modbus Slave on Real-Time tatger

[MarcoMauri]

Hi!

I've problems when debugging an application containing a modbus slave on a real-time target.

The connection is lost when I run the program.

Changing the port from 502 (default value) to other values seems to solve the issue.

Is Labview using the same port for the connection to the RT target?

Tha same problem was notified here, but got no answer:

http://forums.ni.com/t5/LabVIEW/NI-Modbus-TCP-Slave-on-LabVIEW-RT/m-p/1565842#M575497

Regards,

Marco

p.s. We are using the labview modbus libray (http://zone.ni.com/devzone/cda/epd/p/id/4756)

[Loura · Accepted solution]

Hi Marco,

as far as I know port 502 is used only by Modbus Slave (Ethernet) I/O servers to communicate with Modbus Master I/O servers so you should not see any conflict using that port.

(no other LabVIEW services use that port).

You can check whether you deployed duplicate Modbus Slave (Ethernet) I/O servers. Duplicate Modbus Slave (Ethernet) I/O servers cause errors when these I/O servers listen on port 502.

Hope this helps

Clara

[MarcoMauri]

Hi Clara!

You are right: there was a Modbus Slave I/O Server running on the target.

NI Modbus Library seems to check for available ports to avoid collisions, anyhow. I'll give a deeper check when I have time.

thanks!

Marco