I have issues with the COM port recently.
The COM port list does not show up when I click on the "Select Serial Port". I can set the COM port in the setting json and upload to Arduino board without issue. But if I try to open the port, the error message below show up.
Failed to open serial port COM4 due to error: + TypeError: Cannot read property 'close' of null

VScode and arduino extension are updated to latest version. The COM port is not in used
@lamqhoang VSCode insider will repro on this issue, Can you use VSCode stable ?
VSCode insider has been upgraded to node.js >8.0 , This will have breaking changes on the native module on vscode arduino. we will fix this issue next.
This issue is resolved in the latest VSCode insider.
The Nodejs of VSCode insider is reverted to 7.9, so it work well now.
I believe this issue is present again in recent VSCode Insiders versions. Happens to me on 1.31.0-insider for Mac.
Snippet from Developer Tools:
TypeError: Cannot read property 'close' of null
at Object.<anonymous> (bindings.js:27)
at Object.<anonymous> (bindings.js:46)
at Module.t._initNodeRequire.r._compile (loader.js:721)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:722)
...
This exception is generated from the node-usb-native library.
I just installed the standard VSCode (non-insiders) and both the serial port selection dialog and serial monitor are working there. It appears that it is only broken on VSCode Insiders.
@kjcolley7 this issue has been fixed with https://github.com/Microsoft/vscode-arduino/pull/731, and you can use Arduino extension in insiders with next release.
Getting the error in latest insiders version.
Failed to open serial port COM3 due to error: + TypeError: Cannot read property 'close' of null
I'm having the same error as @bluefate .
VSCode-Insiders version: 1.36.0

I found the same mistake
VSCode-Insiders version: 1.36.0-insider

VSCode version: 1.36.0

@lamqhoang @czgtest
Newest VSCode and Arduino plugin.
I'm not able to choose the correct port.
In the Arduino Ide everything works as expected

Explicity defining it in .vscode/adruino.json works
On mac with Arduino/Genuino Uno I use "port": "/dev/cu.usbmodem1421",
My arduino.json
{
"sketch": "Blink.ino",
"port": "/dev/cu.usbmodem1421",
"board": "arduino:avr:uno",
"programmer": "AVRISP mkII"
}
Serial monitor Problem persists tho
Failed to open serial port /dev/cu.usbmodem1421 due to error: + TypeError: Cannot read property 'close' of nu
same here
Have anyone found the solution for this issue?
rollback VSCode to 1.35
Thank you very much, rollback to 1.35 did the trick!
Here's the link if anyone need:
https://code.visualstudio.com/updates/v1_35
Yeah, 1.35 User worked out for me too. Thanks!!
1.36 generates no response when trying to change serial port, but 1.35 and 1.34 crashes the arduino extension when trying to change the port.
Unfortunately 1.40 breaks the com port again. 1.39.2 seems to work. (on Mac OSX at least)
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I'm having the same error as @bluefate .
VSCode-Insiders version: 1.36.0