# Serial loopback, how to get message when no data received

**URL:** https://discourse.nodered.org/t/serial-loopback-how-to-get-message-when-no-data-received/61161
**Category:** General
**Created:** [12 April 2022 10:26 UTC](https://discourse.nodered.org/t/serial-loopback-how-to-get-message-when-no-data-received/61161 "2022-04-12T10:26:48Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![tob84](https://avatars.discourse-cdn.com/v4/letter/t/c6cbf5/32.png) [@tob84](https://discourse.nodered.org/u/tob84)
#### Post date: [12 April 2022 10:26 UTC](https://discourse.nodered.org/t/serial-loopback-how-to-get-message-when-no-data-received/61161/1 "2022-04-12T10:26:48Z")

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[serialloopback.json](https://discourse.nodered.org/uploads/short-url/dVbE8N3E5tVyBEqg7qK19T3bCFm.json) (6.9 KB)

Hi all

I've got a simple serial loopback flow writing a string from COM1-COM2 and COM3-COM4 every 3 seconds, and sending the output from COM3 and COM4 to a TCP out node. This works fine but if I unplug one of my loopback cables I dont get any errors. In this case I want an error message to be sent to the TCP out node i.e. "COM1-2 no response"

This should be simple but I cant see how to do this for looking!

Thanks

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### Author: ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)
#### Post date: [11 June 2022 10:27 UTC](https://discourse.nodered.org/t/serial-loopback-how-to-get-message-when-no-data-received/61161/2 "2022-06-11T10:27:03Z")

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