Debugger restart leaves Azure Functions process or port in use (Attach to .NET, VS Code)

[bueno12223]

Issue Summary

When working with Azure Functions in .NET (isolated process) in Visual Studio Code, using the "Attach to .NET Functions" debugger configuration, the "Restart" button leaves the original function host process or debugger in an inconsistent state.

This causes two major issues:

1. The ports used by the function (e.g., 7071 or 7100) are still occupied.
2. The DLL files are locked by zombie .NET Host processes, leading to MSBuild errors during rebuild.

---

Steps to Reproduce

1. Run an Azure Function (isolated .NET 8) locally in VS Code.
2. Attach to the function using this launch.json config:

{
  "name": "Attach to .NET Functions",
  "type": "coreclr",
  "request": "attach",
  "processId": "${command:azureFunctions.pickProcess}"
}

Click the "Restart" button in the debugger.
VS Code throws:
No process with the specified ID is currently running..
After restart:

The port (7071 or 7100) is still in use.
Rebuilding the project fails with:

MSB3027: Could not copy "...az.dll"
The file is locked by: ".NET Host (PID 10020)"

Workaround

Kill the zombie process manually:

Or kill all dotnet processes:

taskkill /IM dotnet.exe /F

Or restart VS Code completely.

Expected Behavior

Clicking "Restart" should properly detach and re-attach the debugger, cleaning up the old process and freeing any ports or file locks.

It should not leave .NET Host processes hanging or locked on the function DLL.

Environment

OS: Windows 11
VS Code: 1.98.2
Azure Functions Core Tools: 4.0.6821
Azure Functions Extension: 1.16.3
.NET SDK: 8.0.101
Runtime: .NET Isolated
Func port: 7071 / 7100 (default)

[ehuggz1]

@bueno12223 I have a similar issue:

Powershell version 4 Function App
Steps to replicate

• Disconnect from Function App or select Run/Stop Debugging
• VS Code generates error: port 7071 is not available
• Killing func host process in terminal does not release port
• Killing both func host process and powershell process in terminal does not release port

Furthermore
Close VsCode

• Closing and restarting VSCode does release port so debugging can continue, but some memory/processes are not released/killed
• Subsequent restart cycles decrease available memory
• After enough VSCode restarts memory is all consume at which point - restart workstation

Expected functionality

• Stopping Function App Debug Sessions should close ports, kill associated processes, and release memory so that
  Restarting Debugging can resume without errors or consuming increasing amounts of memory and cpu.

[beckerts]

Same issue here.

Pressing Ctrl-C in the terminal tab closes the process correctly.
Message:

• The terminal process "C:\Program Files\PowerShell\7\pwsh.exe -Command func host start" terminated with exit code: 1.
• Terminal will be reused by tasks, press any key to close it.

Selecting the Disconnect icon on the debug menu (Shift-F5) produces the same message in the terminal tab:

• The terminal process "C:\Program Files\PowerShell\7\pwsh.exe -Command func host start" terminated with exit code: 1.
• Terminal will be reused by tasks, press any key to close it.

However on restart (F5) you get the following warning:
C:\Program Files\dotnet\sdk\8.0.407\Microsoft.Common.CurrentVersion.targets(4886,5): warning MSB3026: Could not copy "obj\Debug\net8.0\azurefuncs.dll" to "bin\Debug\net8.0\azurefuncs.dll". Beginning retry 10 in 1000ms. The process cannot access the file 'C:\dev\azurefuncs\bin\Debug\net8.0\azurefuncs.dll' because it is being used by another process. The file is locked by: ".NET Host (11412)"

[EvilConsultant]

Same issue, stopping or restarting a debug session does not release the port and prevents re-running debug.

My launch.json is:
{
"version": "0.2.0",
"configurations": [

{
  "name": "Attach to Python Functions",
  "type": "debugpy",
  "request": "attach",
  "connect": {
    "host": "localhost",
    "port": 9091
  },
  "preLaunchTask": "func: host start",
  
}

]
}

Which I would assume would start it on port 9091, which it doesn't, but I haven't really looked into this - the debugger starts on port 7071.

Subsequent runs of debug return:
Port 7071 is unavailable. Close the process using that port, or specify another port using --port [-p].

Same results as above, restarting VSCODE seems to be the way to restart a debug session.

[misteriks]

I'm having the same issue.
func.exe keeps running and keeps port 7071 occupied.

Workaround for me is: Stop-Process -Id (Get-NetTCPConnection -LocalPort 7071).OwningProcess -Force

[ehuggz1]

Oh that's a nice trick - thanks! Eric Huggins Director, Infrastructure and Cloud Services Check My Meeting ***@***.***/meetingtype/tN-bftiTI0uIVGoqyw07xQ2?bookingcode=05a07af5-243f-445c-8cbc-d1192eefa7fd&anonymous&ep=mLinkFromTile> RightRez, Inc 1-812-21970160 ***@***.*** From: misteriks ***@***.***> Sent: Tuesday, March 25, 2025 10:57 AM To: microsoft/vscode-azurefunctions ***@***.***> Cc: Eric Huggins ***@***.***>; Comment ***@***.***> Subject: Re: [microsoft/vscode-azurefunctions] Debugger restart leaves Azure Functions process or port in use (Attach to .NET, VS Code) (Issue #4416) I'm having the same issue. func.exe keeps running and keeps port 7071 occupied. Workaround for me is: Stop-Process -Id (Get-NetTCPConnection -LocalPort 7071).OwningProcess -Force - Reply to this email directly, view it on GitHub<#4416 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ALF5UPSIJQK6VDTKBQFZQC32WFODVAVCNFSM6AAAAABZOALGXGVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDONJRGU2TGMZRGQ>. You are receiving this because you commented.Message ID: ***@***.******@***.***>> [misteriks]misteriks left a comment (microsoft/vscode-azurefunctions#4416)<#4416 (comment)> I'm having the same issue. func.exe keeps running and keeps port 7071 occupied. Workaround for me is: Stop-Process -Id (Get-NetTCPConnection -LocalPort 7071).OwningProcess -Force - Reply to this email directly, view it on GitHub<#4416 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ALF5UPSIJQK6VDTKBQFZQC32WFODVAVCNFSM6AAAAABZOALGXGVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDONJRGU2TGMZRGQ>. You are receiving this because you commented.Message ID: ***@***.******@***.***>>

[pdimas-aglaia]

Same problem here.

Here another issue about the same topic, with a VSCode task: microsoft/vscode#206607

[nturinski]

Hi all, I appreciate you taking the time to report this.

I looked at the Function Core tools repo, and I think that this issue may be the root cause of the issue.

[NPap0]

Can confirm for python as well, have the same issue.

I'm having the same issue. func.exe keeps running and keeps port 7071 occupied.

Workaround for me is: Stop-Process -Id (Get-NetTCPConnection -LocalPort 7071).OwningProcess -Force

I just ctrl+c the terminal and that seems to restart it normally

[Wpnx330]

Ctrl+C the terminal no longer resolves the issue for me.
In fact, it doesn't even end / detach the running process anymore.

[wilecoyotegenius]

I can confirm the same behavior for nodejs/javascript.

[troyha]

Having a similar issue but with the error:

C:\Program Files\dotnet\sdk\8.0.204\Microsoft.Common.CurrentVersion.targets(4790,5): error MSB3027: Could not copy "obj\Debug\net8.0<projectName>.dll" to "bin\Debug\net8.0<projectName>.dll". Exceeded r
etry count of 10. Failed. The file is locked by: ".NET Host (31624)" [C:\Code\AzureFunctions<projectName><projectName>.csproj]
C:\Program Files\dotnet\sdk\8.0.204\Microsoft.Common.CurrentVersion.targets(4790,5): error MSB3021: Unable to copy file "obj\Debug\net8.0<projectName>.dll" to "bin\Debug\net8.0<projectName>.dll". The p
rocess cannot access the file 'C:\Code\AzureFunctions<projectName>\bin\Debug\net8.0<projectName>.dll' because it is being used by another process. [C:\Code\AzureFunctions<projectName>
<projectName>.csproj]

Restarting VS Code ususally fixes the issue but having to do that after every debug is becoming very frustrating. Especially if I have multiple windows open I have to close them all.

[kirk-quinbar]

I can confirm the same behavior for nodejs/javascript.

same here. assuming this is a bug in the latest release since this used to work just fine in the past?

[gbelenky]

how can we get a previous working release and when will the bug fixed?

[EvilConsultant]

As I workaround, I have had good success with @misteriks workaround. Running this in the powershell window each time after stopping the debugger clears the block:

Stop-Process -Id (Get-NetTCPConnection -LocalPort 7071).OwningProcess -Force

Which you can run manually, or - because I kept forgetting to - add it to launch.json and tasks.json so it runs automatically when the debugger stops.

In launch.json

      "preLaunchTask": "func: host start",
      /* Add the postDebugTask to run the task*/
      "postDebugTask": "Release Blocked Port"

In tasks.json add this task:

tasks : [
/* Don't mess with the other tasks, just add this to the list */
    {
      "label": "Release Blocked Port",
      "type": "shell",
      "command": "powershell.exe -ExecutionPolicy Bypass -Command \"Stop-Process -Id (Get-NetTCPConnection -LocalPort 7071).OwningProcess -Force\"",
      "problemMatcher": []
    }

That way I don't forget to do it. Not a fix but helps keep working around the issue.

[ashikns]

Stop-Process -Id (Get-NetTCPConnection -LocalPort 7071).OwningProcess -Force

The command works when run in powershell, but the VSCode task is not working for me (running in Windows) because it ends up passing "OwningProcess" twice for some reason? Thanks for the command still, it works.