Livereload does not work when using --interface ::1

[WaffleLapkin]

Bug Report

When using zola serve --interface ::1 livereload does not work.

Environment

Zola version: zola 0.20.0

I'm using NixOS, so this is linux, in case that matters for the IP stack.

Expected Behavior

Using --interface ::1 should not affect livereload.

Current Behavior

When making a change in the source, the page is not reloaded. Reloading the page by hand works correctly.

When loading the page (and it seems like periodically later) an error is printed to the console:

Firefox can’t establish a connection to the server at ws://undefined:1024/livereload. livereload.js:1:36894

Step to reproduce

1. Go to a zola blog source
2. Run zola serve --interface ::1
3. Open http://[::1]:1111
4. Open development console and observe the error (you might want to reload the page to see it quicker, if dev console hasn't captured it)
5. Change some page's source
6. Observe that the page isn't updated

[gnpaone]

I've modified code and tested it, it's working fine now. #2869