Socket [::]:123 on Linux listens on IPv4 and IPv6

This will ensure nginx starts up without the following errors messages:
nginx: [emerg] bind() to [::]:443 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:443 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:443 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:443 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:443 failed (98: Address already in use)
nginx: [emerg] still could not bind()

Googling for them leads you to this site:
https://chrisjean.com/2014/02/10/fix-nginx-emerg-bind-to-80-failed-98-address-already-in-use/