# Modbus TCP failed / Proxmox LXC

**URL:** <https://discourse.nodered.org/t/modbus-tcp-failed-proxmox-lxc/99567>\
**Category:** Industrial\
**Tags:** modbus\
**Created:** [3 November 2025 08:14 UTC](https://discourse.nodered.org/t/modbus-tcp-failed-proxmox-lxc/99567 "2025-11-03T08:14:28Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![monardfr](https://avatars.discourse-cdn.com/v4/letter/m/aeb1de/32.png) [@monardfr](https://discourse.nodered.org/u/monardfr)\
**Post date:** [3 November 2025 08:14 UTC](https://discourse.nodered.org/t/modbus-tcp-failed-proxmox-lxc/99567/1 "2025-11-03T08:14:28Z")

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Hi,

I get the following error when trying to retrieve PT100 probe values via Modbus TCP (using modbus contrib).

```auto
Client -> fsm failed state after sending Get More About It By Logging TCP@192.168.1.201:8887 default Unit-Id: 1

```

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/5/9/59e31142a8999a36f397fe16ebe4a92d1f11b690.png)

I tested with modbus poll, and I can successfully connect to the gateway and retrieve the values.

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/6/d/6d62c5fa33f0c66bf1bbdcdb75963295983567c7.png)

Configuration : node-red on contener LXC Proxmox.

Thanks for your help

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<div class="post-metadata">

**Author:** ![Steve-Mcl](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/steve-mcl/32/4826_2.png) [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)\
**Post date:** [3 November 2025 09:29 UTC](https://discourse.nodered.org/t/modbus-tcp-failed-proxmox-lxc/99567/2 "2025-11-03T09:29:04Z")

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> [@monardfr](#):
>
> node-red on contener LXC Proxmox.

Since you have node-red running in a container, this is likely a networking issue.

Try installing node-red-node-ping and ping the modbus IP from within node-red to verify whether it has connectivity.

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<div class="post-metadata">

**Author:** ![monardfr](https://avatars.discourse-cdn.com/v4/letter/m/aeb1de/32.png) [@monardfr](https://discourse.nodered.org/u/monardfr)\
**Post date:** [3 November 2025 10:41 UTC](https://discourse.nodered.org/t/modbus-tcp-failed-proxmox-lxc/99567/3 "2025-11-03T10:41:40Z")

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ping is ok.

192.168.1.201 is my TCP gateway. Port 8887

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/2/7/27d04df4a51e894f61e046842807223ea32b3814.png)

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<div class="post-metadata">

**Author:** ![Steve-Mcl](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/steve-mcl/32/4826_2.png) [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)\
**Post date:** [3 November 2025 11:35 UTC](https://discourse.nodered.org/t/modbus-tcp-failed-proxmox-lxc/99567/4 "2025-11-03T11:35:03Z")

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> [@monardfr](#):
>
> TCP gateway

Can you explain? is this a TCP to RTU/ASCII or something?

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<div class="post-metadata">

**Author:** ![monardfr](https://avatars.discourse-cdn.com/v4/letter/m/aeb1de/32.png) [@monardfr](https://discourse.nodered.org/u/monardfr)\
**Post date:** [3 November 2025 12:44 UTC](https://discourse.nodered.org/t/modbus-tcp-failed-proxmox-lxc/99567/5 "2025-11-03T12:44:07Z")

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Yes,

**With Modbus Pool (software) : OK**

PTA8D08 (PT100 sensor) RS485 Modbus RTU \> NB114 (TCP gateway ) \> Modbus Pool (software, connect mode : modbus RTU over TCP/IP)

work perfectly.

**With Node-Red : ko**

PTA8D08 (PT100 sensor) RS485 Modbus RTU \> NB114 (TCP gateway ) \> Node-red (on Proxmox LXC container)

I made sure that Modbus Pool was not connected to the gateway at the same time as Node-Red.

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<div class="post-metadata">

**Author:** ![monardfr](https://avatars.discourse-cdn.com/v4/letter/m/aeb1de/32.png) [@monardfr](https://discourse.nodered.org/u/monardfr)\
**Post date:** [3 November 2025 13:31 UTC](https://discourse.nodered.org/t/modbus-tcp-failed-proxmox-lxc/99567/6 "2025-11-03T13:31:51Z")

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ok, works now

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/9/0/90c700346f13e0f576bf95d93073ab852a61356b.png)

The gateway was misconfigured. Thanks, you made me redo the entire configuration.

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [17 November 2025 13:32 UTC](https://discourse.nodered.org/t/modbus-tcp-failed-proxmox-lxc/99567/7 "2025-11-17T13:32:47Z")

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