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Luke Puplett
Asked: 2020-02-18 09:51:18 +0800 CST

How to get Ubuntu in WSL 2 to talk to an HTTP server on same Windows host?

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I am running a console app in Windows 10 which has a self-hosted HTTPS server listening on port 44340. It's an ASP.NET Core website (Kestrel) and its perfectly browsable on the Windows side.

I cannot reach this port from within a Windows Subsystem for Linux 2 (WSL2) console running Ubuntu 18.04, testing with curl.

I've tried adding a Windows Firewall rule for that port but it doesn't seem to work.

I've tried via localhost, as well as the two IPs I can see for my machine. One is the real NIC using DHCP and the other is a vEthernet adapter for WSL with a 172.31 address.

networking windows-10 windows-subsystem-for-linux

2 Answers

  1. Here's what I did.

    • Disabled the Windows Firewall (then once proven working, re-enabled and added a rule).
    • Add a hosts file entry on the Windows side for host xyz pointing at my physical NIC IP.
    • Created a self-signed certificate for xyz.
    • Configured Kestrel to listen on the physical NIC IP and load the certificate for xyz
    • Checked the Windows side worked with Chrome.
    • Launched WSL and pinged xyz.
    • Ran curl https://xyz:44340 and observed the failure to validate my self-signed cert.

    That confirms TCP is working, so I'm off to bed. Essentially the blockers were:

    • Firewall.
    • Kestrel not listening on the right IP.
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  2. See guidance here

    https://docs.microsoft.com/en-us/windows/wsl/networking#accessing-windows-networking-apps-from-linux-host-ip

    If you want to access a networking app running on Windows (for example an app running on a NodeJS or SQL server) from your Linux distribution (ie Ubuntu), then you need to use the IP address of your host machine. While this is not a common scenario, you can follow these steps to make it work.

    Obtain the IP address of your host machine by running this command from your Linux distribution: cat /etc/resolv.conf Copy the IP address following the term: nameserver. Connect to any Windows server using the copied IP address. The picture below shows an example of this by connecting to a Node.js server running in Windows via curl.

    You will also need to allow inbound connections to that port in the host. (Through a firewall rule).

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