Reduce number of rpc calls from client

Old: client does an ack rpc every time it receives timeslots, so up
\ to 10 times per second
New: client bundles ack together into the ping rpc, so 1 time per second
Result: a bit less bandwidth usage in multiplayer, bigger benefit when
\ there are more than 2 players

src/game_scene/game_client.gd

@@ -44,6 +44,7 @@ var _time_when_sent_ping: int = 0
 var _ping_history: Array = [0]
 var _received_any_timeslots: bool = false
 var _paused_by_host: bool = false
+var _last_received_timeslot_list: Array = []
 
 
 @export var _game_host: GameHost
@@ -118,8 +119,7 @@ func receive_timeslots(timeslot_list: Dictionary):
 	for tick in timeslot_list.keys():
 		_timeslot_map[tick] = timeslot_list[tick]
 
-	var tick_list: Array = timeslot_list.keys()
-	_game_host.receive_timeslots_ack.rpc_id(1, tick_list)
+	_last_received_timeslot_list = timeslot_list.keys()
 
 
 @rpc("authority", "call_local", "reliable")
@@ -363,6 +363,10 @@ func _get_ping_max() -> float:
 ###     Callbacks     ###
 #########################
 
+# Periodically send a ping from client to host. This ping is
+# used to calculate ping time. It also includes a list of
+# last received timeslots to ack receival of those timeslots
+# and let the host know which timeslots it can stop sending.
 func _on_ping_timer_timeout():
 	_time_when_sent_ping = Time.get_ticks_msec()
-	_game_host.receive_ping.rpc_id(1)
+	_game_host.receive_ping.rpc_id(1, _last_received_timeslot_list)

src/game_scene/game_host.gd

@@ -46,7 +46,7 @@ const TICK_DELTA: float = 1000 / 30.0
 # player. If host hasn't received any responses from player
 # for this long, host will start considering that player to
 # be lagging and will pause game turns.
-const LAG_TIME_MSEC: float = 2000.0
+const LAG_TIME_MSEC: float = 3000.0
 
 @export var _game_client: GameClient
 @export var _hud: HUD
@@ -96,20 +96,6 @@ func _physics_process(_delta: float):
 ###       Public      ###
 #########################
 
-# When player ack's timeslots, host erases ack'd timeslots
-# from queue and stops sending them.
-@rpc("any_peer", "call_local", "reliable")
-func receive_timeslots_ack(tick_list: Array):
-	var peer_id: int = multiplayer.get_remote_sender_id()
-	var player: Player = PlayerManager.get_player_by_peer_id(peer_id)
-	var player_id: int = player.get_id()
-
-	var timeslots_to_send: Dictionary = _player_timeslot_send_queue[player_id]
-
-	for tick in tick_list:
-		timeslots_to_send.erase(tick)
-
-
 @rpc("any_peer", "call_local", "reliable")
 func receive_alive_check_response():
 	var peer_id: int = multiplayer.get_remote_sender_id()
@@ -163,13 +149,19 @@ func receive_timeslot_checksum(tick: int, checksum: PackedByteArray):
 
 
 @rpc("any_peer", "call_local", "reliable")
-func receive_ping():
+func receive_ping(last_received_timeslot_list: Array):
 	var peer_id: int = multiplayer.get_remote_sender_id()
 	var player: Player = PlayerManager.get_player_by_peer_id(peer_id)
 	var player_id: int = player.get_id()
 
 	_update_last_contact_time_for_player(player_id)
 
+#	When player ack's timeslots, host erases ack'd timeslots
+#	from queue and stops sending them.
+	var timeslots_to_send: Dictionary = _player_timeslot_send_queue[player_id]
+	for tick in last_received_timeslot_list:
+		timeslots_to_send.erase(tick)
+
 	_game_client.receive_pong.rpc_id(peer_id)