Fixing suddenly unable to connect to X server in WSL2

Today when I tried to connect to VcXsrv after running it with XLaunch it didn’t work. I’d had it working for months and so was surprised it suddenly stopped working. The reason was simple; the IP subnet WSL2 had changed and so it was now being blocked by a firewall.

Annoyingly there is very little feedback as to why it can’t connect to an XServer. I went back through my previous instructions of setting up an X server in WSL2, but noticed something. When I ran ip addr | grep eth0 it was in the 192.168.0.0/16 subnet. However the WSL2 X server firewall inbound rule I wrote whitelisted the 172.16.0.0/12 subnet. Apparently it can use either private subnet. I’ve now updated the instructions to include both. Because these are private subnets as long as you’re only on networks you trust this should be fairly safe to do.

One upside is servers running newer builds of Windows (after 18945) then WSL2 servers can be accessed through localhost on Windows. This makes testing applications in a browser much easier.