feat: MultiplayerService now provides ping (round-trip time) informat…

…ion for a given connection, closes #877

fxgl-samples/src/main/java/sandbox/net/MultiplayerSample.java

@@ -138,6 +138,8 @@ protected void initGame() {
                     server.setOnConnected(conn -> {
                         connection = conn;
 
+                        getMPService().registerConnection(conn);
+
                         getExecutor().startAsyncFX(() -> {
                             player1 = spawn("player1", 150, 150);
                             getMPService().spawn(connection, player1, "player1");
@@ -149,6 +151,11 @@ protected void initGame() {
                             getMPService().addPropertyReplicationSender(conn, getWorldProperties());
 
                             getMPService().addEventReplicationSender(conn, clientBus);
+
+                            var textPing = getUIFactoryService().newText("", Color.BLUE, 14.0);
+                            textPing.textProperty().bind(getMPService().pingProperty(conn).divide(1000000).asString("Ping: %.0f ms"));
+
+                            addUINode(textPing, 50, 200);
                         });
                     });
 
@@ -162,9 +169,10 @@ protected void initGame() {
                         text.setFont(Font.font(26.0));
                     }, Duration.seconds(5));
 
-
                     var client = getNetService().newTCPClient("localhost", 55555);
                     client.setOnConnected(conn -> {
+                        getMPService().registerConnection(conn);
+
                         getMPService().addEntityReplicationReceiver(conn, getGameWorld());
                         getMPService().addInputReplicationSender(conn, getInput());
                         getMPService().addPropertyReplicationReceiver(conn, getWorldProperties());

fxgl/src/main/kotlin/com/almasb/fxgl/multiplayer/MultiplayerService.kt

@@ -7,7 +7,7 @@
 package com.almasb.fxgl.multiplayer
 
 import com.almasb.fxgl.core.EngineService
-import com.almasb.fxgl.core.collection.PropertyChangeListener
+import com.almasb.fxgl.core.collection.MovingAverageQueue
 import com.almasb.fxgl.core.collection.PropertyMap
 import com.almasb.fxgl.core.collection.PropertyMapChangeListener
 import com.almasb.fxgl.core.serialization.Bundle
@@ -18,6 +18,8 @@ import com.almasb.fxgl.event.EventBus
 import com.almasb.fxgl.input.*
 import com.almasb.fxgl.logging.Logger
 import com.almasb.fxgl.net.Connection
+import javafx.beans.property.ReadOnlyDoubleProperty
+import javafx.beans.property.ReadOnlyDoubleWrapper
 
 /**
  * TODO: symmetric remove API, e.g. removeReplicationSender()
@@ -30,18 +32,56 @@ class MultiplayerService : EngineService() {
 
     private val replicatedEntitiesMap = hashMapOf<Connection<Bundle>, ConnectionData>()
 
+    fun registerConnection(connection: Connection<Bundle>) {
+        val data = ConnectionData(connection)
+        setUpNewConnection(data)
+
+        replicatedEntitiesMap[connection] = data
+    }
+
+    private fun setUpNewConnection(data: ConnectionData) {
+        // register event handler for the given connection
+        // TODO: how to clean up when the connection dies
+        addEventReplicationReceiver(data.connection, data.eventBus)
+
+        data.eventBus.addEventHandler(ReplicationEvent.PING) { ping ->
+            val timeRecv = System.nanoTime()
+            fire(data.connection, PongReplicationEvent(ping.timeSent, timeRecv))
+        }
+
+        data.eventBus.addEventHandler(ReplicationEvent.PONG) { pong ->
+            val timeNow = System.nanoTime()
+            val roundTripTime = timeNow - pong.timeSent
+
+            data.pingBuffer.put(roundTripTime.toDouble())
+            data.ping.value = data.pingBuffer.average
+        }
+    }
+
     override fun onGameUpdate(tpf: Double) {
         if (replicatedEntitiesMap.isEmpty())
             return
 
+        val now = System.nanoTime()
+
         // TODO: can (should) we move this to NetworkComponent to act on a per entity basis ...
         replicatedEntitiesMap.forEach { conn, data ->
+            fire(conn, PingReplicationEvent(now))
+
             if (data.entities.isNotEmpty()) {
                 updateReplicatedEntities(conn, data.entities)
             }
         }
     }
 
+    /**
+     * @return round-trip time from this endpoint to given [connection]
+     */
+    fun pingProperty(connection: Connection<Bundle>): ReadOnlyDoubleProperty {
+        // TODO: if no connection in map
+        return replicatedEntitiesMap[connection]!!.ping.readOnlyProperty
+    }
+
     private fun updateReplicatedEntities(connection: Connection<Bundle>, entities: MutableList<Entity>) {
         val events = arrayListOf<ReplicationEvent>()
 
@@ -73,9 +113,9 @@ class MultiplayerService : EngineService() {
 
         val event = EntitySpawnEvent(networkComponent.id, entityName, entity.x, entity.y, entity.z)
 
-        val data = replicatedEntitiesMap.getOrDefault(connection, ConnectionData())
+        // TODO: if not available
+        val data = replicatedEntitiesMap[connection]!!
         data.entities += entity
-        replicatedEntitiesMap[connection] = data
 
         fire(connection, event)
     }
@@ -237,7 +277,11 @@ class MultiplayerService : EngineService() {
         }
     }
 
-    private class ConnectionData {
+    private class ConnectionData(val connection: Connection<Bundle>) {
         val entities = ArrayList<Entity>()
+        val eventBus = EventBus().also { it.isLoggingEnabled = false }
+
+        val pingBuffer = MovingAverageQueue(1000)
+        val ping = ReadOnlyDoubleWrapper()
     }
 }

fxgl/src/main/kotlin/com/almasb/fxgl/multiplayer/ReplicationEvent.kt

@@ -30,6 +30,9 @@ abstract class ReplicationEvent(eventType: EventType<out ReplicationEvent>) : Ev
 
         @JvmField val PROPERTY_UPDATE = EventType(ANY, "PROPERTY_UPDATE")
         @JvmField val PROPERTY_REMOVE = EventType(ANY, "PROPERTY_REMOVE")
+
+        @JvmField val PING = EventType<PingReplicationEvent>(ANY, "PING")
+        @JvmField val PONG = EventType<PongReplicationEvent>(ANY, "PONG")
     }
 }
 
@@ -70,4 +73,13 @@ class PropertyUpdateReplicationEvent(
 
 class PropertyRemoveReplicationEvent(
         val propertyName: String
-) : ReplicationEvent(PROPERTY_REMOVE)
+) : ReplicationEvent(PROPERTY_REMOVE)
+
+class PingReplicationEvent(
+        val timeSent: Long
+) : ReplicationEvent(PING)
+
+class PongReplicationEvent(
+        val timeSent: Long,
+        val timeReceived: Long
+) : ReplicationEvent(PONG)