Single WSL2 localhost port can't be accessed from Windows side

[peterjuras]

Environment

Windows build number: 10.0.19041.0
Your Distribution version: Ubuntu 20.04
Whether the issue is on WSL 2 and/or WSL 1: Linux version 4.19.84-microsoft-standard (oe-user@oe-host) (gcc version 8.2.0 (GCC)) #1 SMP Wed Nov 13 11:44:37 UTC 2019

Steps to reproduce

1. Create and start a new create-react-app app:

npx create-react-app my-app
cd my-app
npm start

2. Try to access it from the browser using the localhost address: localhost:3000
   -> The browser can't connect
3. Re-start the app by specifying a different port PORT=3001 npm start
   -> The browser can connect

Further details

I expect that this is due to specific configuration on my machine, but I don't know what is wrong. I disabled Windows Firewall and it still doesn't work. Fast Startup is turned off. Accessing the react app through the ip address + port works as expected. Restarting Windows and WSL 2 (multiple times) did not help.

I assume that this issue is similar to issues #5497 and #5298, but I can access servers that are running on different ports (e.g. 5000, 8080, 3001, etc.).

Any workaround would be appreciated. If possible I would like to not need to get into the insider program again, I am hoping I can stay on the stable 2004 version.

[onomatopellan]

Open PowerShell and post the output of:
netsh int ipv4 show excludedportrange protocol=tcp

netsh int ipv4 show dynamicport tcp

[peterjuras]

C:\Users\pjura> netsh int ipv4 show excludedportrange protocol=tcp

Protocol tcp Port Exclusion Ranges

Start Port    End Port
----------    --------
      5357        5357
     50000       50059     *
     55651       55750
     55751       55850
     55991       56090
     56091       56190

* - Administered port exclusions.

C:\Users\pjura> netsh int ipv4 show dynamicport tcp

Protocol tcp Dynamic Port Range
---------------------------------
Start Port      : 49152
Number of Ports : 16384

[onomatopellan]

thanks, tcp dinamic assignation is not the problem then.

Try HOST=0.0.0.0 npm start and see if localhost:3000 works

[peterjuras]

No, sadly HOST=0.0.0.0 npm start does not work.

[onomatopellan]

In Resource Monitor -> Network tab- > Listening ports can you see if there is an exe listening on port 3000?

[peterjuras]

Thanks for helping!
Yes it listing a process, although I have neither anything open with port 3000 or 3100. I also can't find any firewall rule which restricts port 3000 🤔

This is a screenshot of the resource monitor view: https://imgur.com/8qTO4Q6

[onomatopellan]

Some service is using both ports. To know the service on the same Resource Monitor go to CPU tab -> Services, order by PID and look for PID 4248.

[therealkenc]

What Ono said. Or from powershell, using TCP port 5040 as example, which is the Connected Device Platform Service

PS C:\> (Get-WmiObject -Class Win32_Service | where ProcessId -eq (Get-Process -Id (Get-NetTCPConnection -LocalPort 5040).OwningProcess).Id).Name

[peterjuras]

Thanks a lot for the help. 👍 🙏

It appears that the IP Helper service was the culprit and after disabling it the port worked again. I assume this did not have anything to do with WSL 2 then, therefore I'm closing the issue.

[lgyaxx]

What Ono said. Or from powershell, using TCP port 5040 as example, which is the Connected Device Platform Service

PS C:\> (Get-WmiObject -Class Win32_Service | where ProcessId -eq (Get-Process -Id (Get-NetTCPConnection -LocalPort 5040).OwningProcess).Id).Name

Thanks a million for this!

[adolgoff]

Just in case it happened to someone else and there were no such ports open during in-windows inspection, but inside WSL port was listened: it helped me simply to restart WSL by wsl --shutdown {name} and starting it then again.

[damienallen]

Just in case it happened to someone else and there were no such ports open during in-windows inspection, but inside WSL port was listened: it helped me simply to restart WSL by wsl --shutdown {name} and starting it then again.

Restarting WSL was also the solution that I needed! The PS command is still very useful for troubleshooting this though!

[larizzatg]

wsl --shutdown

This solved my issue, thank you

[micskeil]

IP Helper service
Turning off IP helper was the solution for me!

[joshjm]

Ive tried a bunch of other things, but I had to disable IP Helper service to be able to access my stack on localhost:4200 on windows 11, wsl2. weird that this seems to be the issue, i dont think I had this problem with win 10 or running natively on ubuntu.
Seems to the same issue as this fella was having too
I wonder if there is some conflict here with the service that needs a more serious look at.

Easy enough, and safe enough to disable the service through GUI least source:

• launch the build in services app, by searching for services app in the windows search
• navigate/scroll down to IP Helper
• disable the service, and set its startup type to disabled
• reboot

[tekkies]

This worked for me
https://superuser.com/a/1671709/28261

[RunhangShu]

In my case, my port is not allowed. After I add a new rule allowing the port in window firewall, it works. https://pureinfotech.com/open-port-firewall-windows-10/