Cannot connect to websocket using an IPv6 address

[jacopofar]

Probably related with #39331 but on the client side

Godot version:
3.2.3 stable

OS/device including version:
macOS 10.15

Issue description:
When connecting to a server exposing a websocket, the connection does not work if I specify ws://[:.1]:4000 and run the game as a native app. If I export to HTML5 and run in the browser, the connection is established without issues.

If I use 127.0.0.1 the connection can be created both in HTML5 and in the native app, while with localhost only the HTML5 version works.

Steps to reproduce:

You can use the demo for Godot Phoenix channels here, accidentally it already implements this behavior and allows to try different hostnames from its UI

[jonbonazza]

@jacopofar what is localhost aliased to on your machine?

[jacopofar]

ifconfig says

lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
	options=1203<RXCSUM,TXCSUM,TXSTATUS,SW_TIMESTAMP>
	inet 127.0.0.1 netmask 0xff000000
	inet6 ::1 prefixlen 128
	inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
	nd6 options=201<PERFORMNUD,DAD>

pinging and nslookup report 127.0.0.1