[MP] Let MultiplayerAPI handle packet relaying and peer signaling.

MultiplayerPeer changes:

- Adds is_server_relay_supported virtual method

Informs the upper MultiplayerAPI layer if it can signal peers connected
to the server to other clients, and perform packet relaying among them.

- Adds get_packet_channel and get_packet_mode virtual methods

Allows the MultiplayerAPI to retrieve the channel and transfer modes to
use when relaying the last received packet.

SceneMultiplayerPeer changes:

- Implement peer signaling and packet relaying when the MultiplayerPeer
  advertise they are supported.

ENet, WebRTC, WebSocket changes:

- Removed custom code for relaying from WebSocket and ENet, and let it
  be handled by the upper layer.
- Update WebRTC to split create_client, create_server, and create_mesh,
  with the latter behaving like the old initialize with
  "server_compatibility = false", and the first two supporting the upper
  layer relaying protocol.

1 files changed, 26 insertions, 13 deletions

diff --git a/modules/webrtc/doc_classes/WebRTCMultiplayerPeer.xml b/modules/webrtc/doc_classes/WebRTCMultiplayerPeer.xml
index 927888fe21..0b42c6ed35 100644
--- a/modules/webrtc/doc_classes/WebRTCMultiplayerPeer.xml
+++ b/modules/webrtc/doc_classes/WebRTCMultiplayerPeer.xml
@@ -6,7 +6,7 @@
 	<description>
 		This class constructs a full mesh of [WebRTCPeerConnection] (one connection for each peer) that can be used as a [member MultiplayerAPI.multiplayer_peer].
 		You can add each [WebRTCPeerConnection] via [method add_peer] or remove them via [method remove_peer]. Peers must be added in [constant WebRTCPeerConnection.STATE_NEW] state to allow it to create the appropriate channels. This class will not create offers nor set descriptions, it will only poll them, and notify connections and disconnections.
-		[signal MultiplayerPeer.connection_succeeded] and [signal MultiplayerPeer.server_disconnected] will not be emitted unless [code]server_compatibility[/code] is [code]true[/code] in [method initialize]. Beside that data transfer works like in a [MultiplayerPeer].
+		[signal MultiplayerPeer.connection_succeeded] and [signal MultiplayerPeer.server_disconnected] will not be emitted unless the peer is created using [method create_client]. Beside that data transfer works like in a [MultiplayerPeer].
 		[b]Note:[/b] When exporting to Android, make sure to enable the [code]INTERNET[/code] permission in the Android export preset before exporting the project or using one-click deploy. Otherwise, network communication of any kind will be blocked by Android.
 	</description>
 	<tutorials>
@@ -28,6 +28,31 @@
 				Close all the add peer connections and channels, freeing all resources.
 			</description>
 		</method>
+		<method name="create_client">
+			<return type="int" enum="Error" />
+			<param index="0" name="peer_id" type="int" />
+			<param index="1" name="channels_config" type="Array" default="[]" />
+			<description>
+				Initialize the multiplayer peer as a client with the given [code]peer_id[/code] (must be between 2 and 2147483647). In this mode, you should only call [method add_peer] once and with [code]peer_id[/code] of [code]1[/code]. This mode enables [method MultiplayerPeer.is_server_relay_supported], allowing the upper [MultiplayerAPI] layer to perform peer exchange and packet relaying.
+				You can optionally specify a [code]channels_config[/code] array of [enum MultiplayerPeer.TransferMode] which will be used to create extra channels (WebRTC only supports one transfer mode per channel).
+			</description>
+		</method>
+		<method name="create_mesh">
+			<return type="int" enum="Error" />
+			<param index="0" name="peer_id" type="int" />
+			<param index="1" name="channels_config" type="Array" default="[]" />
+			<description>
+				Initialize the multiplayer peer as a mesh (i.e. all peers connect to each other) with the given [code]peer_id[/code] (must be between 1 and 2147483647).
+			</description>
+		</method>
+		<method name="create_server">
+			<return type="int" enum="Error" />
+			<param index="0" name="channels_config" type="Array" default="[]" />
+			<description>
+				Initialize the multiplayer peer as a server (with unique ID of [code]1[/code]). This mode enables [method MultiplayerPeer.is_server_relay_supported], allowing the upper [MultiplayerAPI] layer to perform peer exchange and packet relaying.
+				You can optionally specify a [code]channels_config[/code] array of [enum MultiplayerPeer.TransferMode] which will be used to create extra channels (WebRTC only supports one transfer mode per channel).
+			</description>
+		</method>
 		<method name="get_peer">
 			<return type="Dictionary" />
 			<param index="0" name="peer_id" type="int" />
@@ -48,18 +73,6 @@
 				Returns [code]true[/code] if the given [code]peer_id[/code] is in the peers map (it might not be connected though).
 			</description>
 		</method>
-		<method name="initialize">
-			<return type="int" enum="Error" />
-			<param index="0" name="peer_id" type="int" />
-			<param index="1" name="server_compatibility" type="bool" default="false" />
-			<param index="2" name="channels_config" type="Array" default="[]" />
-			<description>
-				Initialize the multiplayer peer with the given [code]peer_id[/code] (must be between 1 and 2147483647).
-				If [code]server_compatibilty[/code] is [code]false[/code] (default), the multiplayer peer will be immediately in state [constant MultiplayerPeer.CONNECTION_CONNECTED] and [signal MultiplayerPeer.connection_succeeded] will not be emitted.
-				If [code]server_compatibilty[/code] is [code]true[/code] the peer will suppress all [signal MultiplayerPeer.peer_connected] signals until a peer with id [constant MultiplayerPeer.TARGET_PEER_SERVER] connects and then emit [signal MultiplayerPeer.connection_succeeded]. After that the signal [signal MultiplayerPeer.peer_connected] will be emitted for every already connected peer, and any new peer that might connect. If the server peer disconnects after that, signal [signal MultiplayerPeer.server_disconnected] will be emitted and state will become [constant MultiplayerPeer.CONNECTION_CONNECTED].
-				You can optionally specify a [code]channels_config[/code] array of [enum MultiplayerPeer.TransferMode] which will be used to create extra channels (WebRTC only supports one transfer mode per channel).
-			</description>
-		</method>
 		<method name="remove_peer">
 			<return type="void" />
 			<param index="0" name="peer_id" type="int" />