# Simulating Multiple Modbus Slaves
**URL:** https://discourse.nodered.org/t/simulating-multiple-modbus-slaves/69214
**Category:** General
**Created:** [18 October 2022 18:27 UTC](https://discourse.nodered.org/t/simulating-multiple-modbus-slaves/69214 "2022-10-18T18:27:37Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@vigalent](https://discourse.nodered.org/u/vigalent)
#### Post date: [18 October 2022 18:27 UTC](https://discourse.nodered.org/t/simulating-multiple-modbus-slaves/69214/1 "2022-10-18T18:27:37Z")
I'm working on a project whereby I'm using a IOT gateway monitoring multiple systems / sensors that runs an instance of Node-Red.
I'm pulling data back and exposing point values via ModbusTCP (using [node-red-contrib-modbus) to a 3rd party modbus master, but I need to write said data to multiple modbus slaves.
Using the flex write node and have the following code from 2 different functions attempting to write to 2 different slaves. But it seems the flex write is writing to both slaves despite the "unitid" being different in each function?
Does anyone know where I'm going wrong?
```auto
var coil = msg.payload;
msg.payload = {
'value': coil,
'fc': 5,
'unitid': 1,
'address': 1,
'quantity': 1
}
return msg
```
and
```auto
var coil = msg.payload;
msg.payload = {
'value': coil,
'fc': 5,
'unitid': 2,
'address': 1,
'quantity': 1
}
return msg
```
---
### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [17 December 2022 18:28 UTC](https://discourse.nodered.org/t/simulating-multiple-modbus-slaves/69214/2 "2022-12-17T18:28:06Z")
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