How to listen to connections from both IPv4 and IPv6 addresses

This came up on the forums but is worth posting here as well for visibility. The default Vapor template listens on 127.0.0.1 which only allows local IPv4 connections. If you want to allow connections from other devices you need to set the hostname to 0.0.0.0. However, again this only accepts IPv4 connections. If you want to allow IPv4 and IPv6 connections you can set the hostname to ::. This will accept connections from all addresses on both IP stacks.

Thanks to Cory for posting the answer!