# Serial port COM4 error: Error: Opening COM4: File not found
**URL:** https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756
**Category:** General
**Created:** [15 August 2021 17:49 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756 "2021-08-15T17:49:30Z")
**Posts on this page:** 16
**Page:** 1
### Author:  [@owmath](https://discourse.nodered.org/u/owmath)
#### Post date: [15 August 2021 17:49 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/1 "2021-08-15T17:49:31Z")
Good afternoon, i have a problem starting my node-red.
when I run the command to open "node-red", it shows me serial port COM4 error: Error: Opening COM4: File not found.
Before this error happened, I managed to perform an LED test connected with the Arduino and everything worked correctly, when I went to perform a test with the DHT22 sensor and then closed my Node-Red, this error appears.
The Arduino IDE works normally with the COM4 port, I can normally program the program on it and run it.
I want to open my Node-Red, how can I solve this?
Thanks, Matheus
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [15 August 2021 17:59 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/2 "2021-08-15T17:59:17Z")
Does device manager show you have a COM4?
Is there any application still open & accessing COM4 (e.g. is Arduino IDE still open when you start node-red)
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### Author:  [@owmath](https://discourse.nodered.org/u/owmath)
#### Post date: [15 August 2021 18:05 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/3 "2021-08-15T18:05:17Z")
Yes, the manager recognizes the COM4 input so much that I can run the program directly in the Arduino IDE.
There is no application open when I try to start Node-Red..
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [15 August 2021 18:15 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/4 "2021-08-15T18:15:10Z")
> [@owmath](#):
>
> There is no application open when I try to start Node-Red
I would restart your PC - potentially something has a hold on the port.
Alternatively, try this: [https://www.equisys.com/Support/Technotes/howto-identifying-which-process-is-using-the-serial-port](https://www.equisys.com/Support/Technotes/howto-identifying-which-process-is-using-the-serial-port)
* * *
PS,
- what version of `node` and `node-red` are you running?
- what does `npm list serialport` show...
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### Author:  [@owmath](https://discourse.nodered.org/u/owmath)
#### Post date: [15 August 2021 18:18 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/5 "2021-08-15T18:18:53Z")
check this screenshot 😢
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [15 August 2021 18:19 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/6 "2021-08-15T18:19:58Z")
you did not CD into **your** `.node-red` folder - look at my screenshot.
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### Author:  [@owmath](https://discourse.nodered.org/u/owmath)
#### Post date: [15 August 2021 18:25 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/7 "2021-08-15T18:25:13Z")
is the command to enter the folder right? I can't get into node-red CD
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [15 August 2021 19:04 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/8 "2021-08-15T19:04:28Z")
no.
from your earlier screenshot i see your user name is `user`
So enter
`cd c:\users\user\.node-red`
then
`npm list serialport`
ALSO - you never stated what version of node-red you are running - it is listed in the console when you start node-red (it is missing from the opt your first screenshot)
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### Author:  [@owmath](https://discourse.nodered.org/u/owmath)
#### Post date: [15 August 2021 19:06 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/9 "2021-08-15T19:06:07Z")
there's the error, how do I fix it?
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [15 August 2021 19:07 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/10 "2021-08-15T19:07:06Z")
Sorry, its a typo by me.
So enter
`cd c:\users\user\.node-red`
then
`npm list serialport`
ALSO - you never stated what version of node-red you are running - it is listed in the console when you start node-red (it is missing from the top your first screenshot)
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### Author:  [@owmath](https://discourse.nodered.org/u/owmath)
#### Post date: [15 August 2021 19:08 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/11 "2021-08-15T19:08:21Z")
check
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [15 August 2021 19:15 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/12 "2021-08-15T19:15:20Z")
ok, so do you have any arduino nodes in your flows?
use ctrl-f to search node-red flows for `aurduino`
Perhaps you have added a node and set it to use COM4?
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### Author:  [@owmath](https://discourse.nodered.org/u/owmath)
#### Post date: [15 August 2021 19:17 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/14 "2021-08-15T19:17:25Z")
Yes, I used Arduino node and configured to use COM4, how do I delete? I can't get into the dashboard
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### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [15 August 2021 19:18 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/15 "2021-08-15T19:18:21Z")
Its not dashboard (its the node-red editor)
start node-red in safe mode
```auto
node-red --safe
```
find and delete, then deploy.
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### Author:  [@owmath](https://discourse.nodered.org/u/owmath)
#### Post date: [15 August 2021 19:21 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/16 "2021-08-15T19:21:40Z")
incredible friend, thank you very much you found the solution! thank you so much 🤩
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### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [29 August 2021 19:22 UTC](https://discourse.nodered.org/t/serial-port-com4-error-error-opening-com4-file-not-found/49756/17 "2021-08-29T19:22:31Z")
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