Unofficial Godot 4.0 Pre-Alpha Multiplayer Changes Overview

godot4multiplayergist.md

Unofficial Godot 4.0 Pre-Alpha Multiplayer Changes Overview

Note: Everything may still change, if you need something stable and documented to depend on, use Godot 3.x/stable.

Last updated: 2021-10-06

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Relevant Pull Requests (look at all):

• https://godotengine.org/article/multiplayer-changes-godot-4-0-report-1
• https://github.com/godotengine/godot/commit/24a949ea1154a2298e6898c53fdb75178affe098
• Multiplayer renames/simplification: godotengine/godot#52480
• Spawn/despawn sync: godotengine/godot#51097 and godotengine/godot#51534
• State sync: godotengine/godot#51788
• Renames: godotengine/godot#51481 and godotengine/godot#50398
• close_connection() is silent now: godotengine/godot#52342
• By default, all peers can now call RPC methods, whereas previously it was only master: godotengine/godot#51301
• Channels are now supported in MultiplayerPeer: godotengine/godot#51005
• Mesh networking and lowlevel wrappers for ENet: godotengine/godot#50710
• RSETs got removed: godotengine/godot#49221
• Tons of fixes and improvements :)
• MultiplayerAPI is now used instead of things like signals being on the SceneTree directly: https://docs.godotengine.org/de/latest/classes/class_multiplayerapi.html
• network has been removed where possible in MultiplayerAPI due to redundancy, e.g. multiplayer.is_network_server() is now just multiplayer.is_server(), exception are the methods in Node, where multiplayer is used instead, see below:
• Node.set_network_master() is now Node.set_multiplayer_authority()
• The TransferMode and RPCMode enums are now bound as core constants, which means instead of MultiplayerAPI.RPC_MODE_ANY you can just use RPC_MODE_ANY

Setup peer

# Create peer
var peer = ENetMultiplayerPeer.new()

# Connect some signals if you want them
peer.peer_connected.connect(_peer_connected)
peer.peer_disconnected.connect(_peer_disconnected)
peer.connection_failed.connect(_connection_failed)
peer.connection_succeeded.connect(_connection_succeeded)
# (You can also connect to get_tree().multiplayer.peer_connected and so on,
# that works even while the peer is null)

# peer.create_server(SERVER_PORT)
peer.create_client(SERVER_IP, SERVER_PORT)

# Assign peer to multiplayer API
# Multiplayer API now has most relevant functions, have a look at get_tree().multiplayer
get_tree().multiplayer.network_peer = peer

RPCs are @rpc annotations now

RSETs are gone, just use RPCs now.

You use the @rpc annotation to denote RPC functions. You can use arguments with that annotation for configuration, in any order. Arguments are:

• sync/nosync (whether calls are called locally too, or only remote)
• any/auth (whether the RPC can be called by any peer or only auth, the authority (previously master)
• reliable/unreliable/ordered (transfer mode)

Examples:

remote func test() becomes

@rpc
test()

remotesync func test() becomes

@rpc(any, sync)
test()

mastersync would now be @rpc(auth, sync).

You can also still use Node.rpc_config():

rpc_config(&'move_and_slide', RPC_MODE_ANY)

Using the new multiplayer spawning and syncing

This enabled scene spawning/syncing replication for the scenes "Player" and "Box". For both, spawns are synced, so if you .instantiate() them and add them to the scene, that gets done on all other peers automatically as well, same for .queue_free()ing/deleting them. For "Player", position is kept synced as well, so if you move, position gets updated on peers. For real use, you want to use a custom RPC for movement (to be able to interpolate the position and smooth updates). But this is useful to keep less important things synchronized.

func _ready():
	_replication_setup(Player, ["position"], true)
	_replication_setup(Box, ["position"])

func _replication_setup(scene : PackedScene, params : Array, sync : bool = false):
  	# Scenes are identified using the new resource UIDs
	var id = ResourceLoader.get_resource_uid(scene.resource_path)
	
  	# Enable spawn/despawn syncing
	multiplayer.replicator.spawn_config(
		id,
		MultiplayerReplicator.REPLICATION_MODE_SERVER,
		params
	)
	
	if sync:
    		# Enable property syncing
		multiplayer.replicator.sync_config(id, 16, params)