Listen 127.0.0.1:443 Listen [::]:443 These two config lines are valid, and should work together. Httpd is expected to bind on the sole IPv4 address I mentionned, and on [::]. They result with httpd refusing to start. (98)Address already in use: make_sock: could not bind to address [::]:443 This bug can also be reproducted on 2.2.22. I tend to suspect it has been around since IPv6 was implemented into httpd at all.
Listen 0.0.0.0:443 Listen [::]:443 These do work and might constitue a workaround on some configurations.
This is the default behaviour when IPv4-mapped IPv6 addresses are enabled, since binding on port 443 on both addresses conflicts at kernel level if that is true. With r1879106 it is now possible to change this behaviour.