Multicast, more network interfaces info

[Faless]

In this PR:

• New get_local_interfaces method returns informations about network cards (names, ips)
• UDP Multicast support via join/leave_multicast_group methods in PacketPeerUDP.
  In the future, adding a single source (and blocking a source) could be similarly supported.

Test project (run on multiple machines, same network. Unless firewall blocks, should work).

Tested Win<->Android, Linux<->Android, and compiles on *BSD too. UWP does not really support getting interfaces in all its variants, so for now it returns a fake interfaces for each ip addresses discovered via GetHostNames.

extends Control

const ADDR = "224.0.0.1"
const ADDRV6 = "ff02::114"
var _udp = PacketPeerUDP.new()
var _id = 0

func _ready():
	seed(OS.get_unix_time())
	_id = randi()
	_udp.listen(8080)

	for iface in IP.get_local_interfaces():
		_log("=== IFACE ===")
		_log("Name: %s" % iface.name)
		_log("Friendly: %s" % iface.friendly)
		_log("Addresses: %s" % str(iface.addresses))
		_log("Index: %s" % str(iface.index))
		for ip in iface.addresses:
			if "." in ip:
				_log("Adding interface %s to IPv4 multicast group %s -> %d" % [iface.name, ADDR, _udp.join_multicast_group(ADDR, iface.name)])
			else:
				_log("Adding interface %s to IPv6 multicast group %s -> %d" % [iface.name, ADDRV6, _udp.join_multicast_group(ADDRV6, iface.name)])

func _process(delta):
	while _udp.get_available_packet_count():
		_log(_udp.get_packet().get_string_from_utf8())

func _log(msg):
	print(msg)
	$TextEdit.text += str(msg) + "\n"

func _on_Button_pressed():
	_udp.set_dest_address(ADDR, 8080)
	_udp.put_packet(("ciao IPv4! %d" % _id).to_utf8())
	_udp.set_dest_address(ADDRV6, 8080)
	_udp.put_packet(("ciao IPv6! %d" % _id).to_utf8())

[akien-mga]

Thanks!