# Serial Port COM3 does not receive or send any thing

**URL:** <https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113>\
**Category:** General\
**Created:** [4 March 2023 17:32 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113 "2023-03-04T17:32:02Z")\
**Posts on this page:** 13\
**Page:** 1

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**Author:** ![Student](https://avatars.discourse-cdn.com/v4/letter/s/ecc23a/32.png) [@Student](https://discourse.nodered.org/u/Student)\
**Post date:** [4 March 2023 17:32 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113/1 "2023-03-04T17:32:02Z")

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Hi! Please can someone help me.  
Only debug 10 displays the data, but debug 11 doesn't display any thing.  
My flow is as follows:

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/9/a/9af8ca9780f6a43d1e381be907169b3caa580057.png)  
Thank you very much for youy help

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**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:** [4 March 2023 17:45 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113/2 "2023-03-04T17:45:50Z")

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Do you have something physically attached to COM3?

Have you tried using putty or another hyperterminal to see if it responds to sending it `30`?

Are you using a known working serial cable?

Have you tried the Serial Request node?

Do you have the settings correct on the COM config?

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**Author:** ![Student](https://avatars.discourse-cdn.com/v4/letter/s/ecc23a/32.png) [@Student](https://discourse.nodered.org/u/Student)\
**Post date:** [4 March 2023 17:52 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113/3 "2023-03-04T17:52:59Z")

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No, I have nothing physically attached to COM3.  
The settings are correct on the COM3 config.  
I do not tried anything else.  
I just want to make a simulation: write 30 on the port com3 and read its content.  
I am a beginner.  
Thank you very much for your help.

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**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:** [4 March 2023 17:55 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113/4 "2023-03-04T17:55:49Z")

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> [@Student](#):
>
> No, I have nothing physically attached to COM3.

Then this is your issue. you either need a device or a loop back or a pair of virtual com ports that are "wired".

What you are doing is transmitting data to a COM port TX pin & because it is not connected to anything, the data bits are falling out the end all over your desk (a metaphor I hope you understand)

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**Author:** ![Student](https://avatars.discourse-cdn.com/v4/letter/s/ecc23a/32.png) [@Student](https://discourse.nodered.org/u/Student)\
**Post date:** [4 March 2023 18:01 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113/5 "2023-03-04T18:01:42Z")

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Thank you very much for your response.  
Please, is there a way to simulate data from e.g. a temperature sensor without having (a physical sensor) and capture it (the data) on a serial port, then display it for educational purposes?

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**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:** [4 March 2023 18:12 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113/6 "2023-03-04T18:12:39Z")

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Must it be a serial port?

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**Author:** ![Student](https://avatars.discourse-cdn.com/v4/letter/s/ecc23a/32.png) [@Student](https://discourse.nodered.org/u/Student)\
**Post date:** [4 March 2023 18:16 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113/7 "2023-03-04T18:16:51Z")

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Not necessarily.

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**Author:** ![Student](https://avatars.discourse-cdn.com/v4/letter/s/ecc23a/32.png) [@Student](https://discourse.nodered.org/u/Student)\
**Post date:** [4 March 2023 18:18 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113/8 "2023-03-04T18:18:23Z")

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It is to stimulate a simple use case of IoT.

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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:** [4 March 2023 18:20 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113/9 "2023-03-04T18:20:33Z")

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OK, so if it MUST be serial then, on windows, you can use com0com to setup a pair of virtual com ports.  
e.g. virtual com 8 \<- -\> com 9  
then you write to com 9, it appears in com 8, you respond to com 8 and the response appears on com 9

NOTE: This is by no means simple and serial devices are becoming less and less common - so in my opinion, not typical of many of todays IoT setups.

* * *

If you just want to simulate sensors, then I would recommend using MQTT (publish random sensor values over MQTT then subscribe to the same topic and then use the values on a dashboard or whatever you need to do do.)

MQTT is pretty much the defacto means of publishing IoT data at this present time.

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<div class="post-metadata">

**Author:** ![Student](https://avatars.discourse-cdn.com/v4/letter/s/ecc23a/32.png) [@Student](https://discourse.nodered.org/u/Student)\
**Post date:** [4 March 2023 18:30 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113/10 "2023-03-04T18:30:30Z")

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Honestly, thank you very much for your help and your time.

I will try it all and see if I will succeed in working this.

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**Author:** ![Colin](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/colin/32/17040_2.png) [@Colin](https://discourse.nodered.org/u/Colin)\
**Post date:** [4 March 2023 21:16 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113/11 "2023-03-04T21:16:57Z")

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If you want to learn more about MQTT then see this tutorial [MQTT Essentials - All Core Concepts explained](https://www.hivemq.com/mqtt-essentials/)

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<div class="post-metadata">

**Author:** ![Student](https://avatars.discourse-cdn.com/v4/letter/s/ecc23a/32.png) [@Student](https://discourse.nodered.org/u/Student)\
**Post date:** [6 March 2023 02:49 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113/12 "2023-03-06T02:49:20Z")

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Thank you very much Colin for your help.  
I appreciate.

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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:** [5 May 2023 02:49 UTC](https://discourse.nodered.org/t/serial-port-com3-does-not-receive-or-send-any-thing/76113/13 "2023-05-05T02:49:27Z")

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