AdvancedHMI as Modbus TCP Server

I tried to use AdvancedHMI as a Modubius Client and it does poll the data from a Modbus server. But I am unable to use AdvancedHMI as a server, does anybody knows how?

The AdvancedHMI Modbus driver will only act as a Client (Master) and not a Server (Slave).
What is the application that you would need this to act as a server?
If you are using Modbus TCP you can have more than one Client.

Regards,
Garry

Thank you Gary.

I am working on monitoring/operating PLCs over internet. For safety reasons I prefer the PLC reads not to write to the PLC.

By the way, anyone knows how AdvancedHMI is performing on a Intel® Atom™ E3845, Quad core Advantech Fanless Panel PC?

It's runs on Raspberry Pi so it will run on 4 Core Atom without any problem.

Great! Thank you!

So having the AdvancedHMI act as a Client is no problem. You just make sure that you do not program any writing instructions in AdvancedHMI.

AlecTek said:

Thank you Gary.

I am working on monitoring/operating PLCs over internet. For safety reasons I prefer the PLC reads not to write to the PLC.

Click to expand...

Modbus does not have a read-only mode, if you make the Modbus port of the server accessible on the internet, anyone who connects can also change data.

That is very insecure, we just have to see a log of any firewall of a public IP to verify that every day hundreds of attempts to connect to different ports are received.

Use a VPN or a protocol with security capabilities like OPC UA.

lfe said:

Modbus does not have a read-only mode, if you make the Modbus port of the server accessible on the internet, anyone who connects can also change data.

That is very insecure, we just have to see a log of any firewall of a public IP to verify that every day hundreds of attempts to connect to different ports are received.

Use a VPN or a protocol with security capabilities like OPC UA.

Click to expand...

This is the point. I don't like to open a port of the plant network. As to the AdvancedHMI over the internet, there are some ways to increase the security. That's why I would like to let the PLC be the client and the AdvancedHMI be the server.

https://www.automationdirect.com/stride

What about something like StrideLinx. This would take care of your security.
Just a thought.
Regards,

Swapping client and server roles doesn't really add security, it just moves the risk from your PLC to your advancedHMI server.

If the connection is not protected by a VPN and firewall then anyone can connect and write to your modbus server. That's still a very undesirable condition.

VPNs are not that expensive to set up.

If you want an extra layer of protection, add a Protocol aware transparent firewall such as Moxa EDR. You can restrict which modbus commands are allowed or blocked, essentially making "read only" possible.

I would still keep it all behind a VPN. Devices with very limited bandwidth like PLCs are susceptible to Denial of Service attacks.