Fallback to sms when modbus tcp trough VPN fails

[ghoul]

Greetings,

I have a configuration like this :

TRB-NR reads Logo-NR - High or Low. Then TRB-NR sends a modbus write request over the public ip(rms vpn hub) to TRB-PS to toggle Output4, Logo-PS is polling Output4(trb-ps) to check if its high or low, and activate M4 correspondingly on LOGO-PS.

But now i need to have a fallback, so when M4 and I2 on the Logo-PS are 0, it will the send the HIGH/LOW trough sms or something else.

Does anyone have some examples or explanation on how to configure this.

Thanks in Advance,

Ghoul

[Matas]

Hello,

Just so it’s easier to understand your current configuration & your desired configuration, could you possibly provide a drawn topology with the IP addresses of the devices, the data being sent, and what needs to happen?

More or less, from what I’ve understood, currently - TRB no. 1 reads a value from a device called “Logo-NR” (? what device is it) → Sends a Modbus write request over the VPN Hub to TRB no. 2 to toggle an output. To the output, there’s another device connected (?) which activates M4 (? is it another device? is it the name of an input/output?)

And you want it to also send an SMS message of the status of whether it is currently high/low?

As you can see, I’m having a bit of trouble fully understanding the issue, so clarification would be highly appreciated.

Regards,
M.

[ghoul]

So currently TRB1 reads a value (1/0) from Marker3 on Logo1 via modbus tcp

And it continuesly sends the status(1/0) to TRB2 via its Public IP and toggles Pin4 correspondely.(via modbus tcp)

Logo2 will then toggle Marker 4 on basis of the High1 or Low0 Output4.

But as a fallback for when the vpn is down and the signal of TRB1 cant reach TRB2

i’d want it to start the same flow but trough SMS

(Logo is a siemens PLC and a marker is a flag that sees 1/0 and i access it trough its modbus register number)

Thanks for answering. ill upload a better topology tommorow.

[ghoul]

[ghoul]

Here’s chatgpt’s clarification :

Current Setup (for clarity):

• TRB1:

  • Reads Marker3 (1/0) from LOGO1 via Modbus TCP.

  • Sends that 1/0 to TRB2 (Public IP) via Modbus TCP.

• TRB2:

  • Sets Output Pin 4 based on that value.

  • LOGO2 reads the pin status (high/low) and toggles Marker4 accordingly.

---

New Requirement: Fallback via SMS if VPN / TCP fails

So, if Modbus over TCP fails (likely due to VPN outage), you want:

1. TRB1 to send an SMS with the state of Marker3 (1/0).

2. TRB2 to receive that SMS.

3. TRB2 to parse the SMS and toggle Pin 4 accordingly.

If TRB1 can’t reach TRB2 (VPN down), send the status (1/0) from Marker3 on LOGO1 to TRB2 some other way – so TRB2 can still toggle Output 4 correctly

[Matas]

Hello,

After reviewing the clarification (thank you for that), I can confirm that your setup will require a custom script to be able to achieve what you want. We currently don’t have a trigger in the Event Juggler that would send an SMS when the OpenVPN connection is down (or Modbus for that matter).

As custom scripts are out of our scope, I can only recommend looking into the following Wiki to get to know the syntax of our scripts: User Scripts examples - Teltonika Networks Wiki

Regards,
M.