1. import akka.actor._
2.  
3.  
4.  
5. case class Ping(target: ActorRef)
6.  
7. case class Pong(target: ActorRef)
8.  
9. case class Zong(target: ActorRef)
10.  
11.  
12.  
13. class Player(private val NUMBER_OF_RALLIES: Int) extends Actor{
14.  
15.   private var receivedBallCounter = 0
16.  
17.  
18.  
19.   def receive = {
20.  
21.       case Ping(targetPlayerRef) => {
22.  
23.         println("ping")
24.  
25.         receivedBallCounter += 1
26.  
27.  
28.  
29.         if ( receivedBallCounter < NUMBER_OF_RALLIES ) {
30.  
31.           targetPlayerRef ! Pong(self)
32.  
33.         }
34.  
35.         else {
36.  
37.           targetPlayerRef ! Pong(self)
38.  
39.           targetPlayerRef ! PoisonPill
40.  
41.         }
42.  
43.       }
44.  
45.  
46.  
47.       case Pong(targetPlayerRef) => {
48.  
49.         println("pong")
50.  
51.         receivedBallCounter += 1
52.  
53.  
54.  
55.         if ( receivedBallCounter < NUMBER_OF_RALLIES ) {
56.  
57.           targetPlayerRef ! Ping(self)
58.  
59.         }
60.  
61.         else {
62.  
63.           targetPlayerRef ! PoisonPill
64.  
65.         }
66.  
67.       }
68.  
69.  
70.  
71.       case _ => {
72.  
73.         println("Unhandled message")
74.  
75.       }
76.  
77.   }
78.  
79. }
80.  
81.  
82.  
83. val NUMBER_OF_RALLIES = 5
84.  
85. val actorSystem = ActorSystem("PingPongTraining")
86.  
87. val player1 = actorSystem.actorOf(Props(classOf[Player], NUMBER_OF_RALLIES))
88.  
89. val player2 = actorSystem.actorOf(Props(classOf[Player], NUMBER_OF_RALLIES))
90.  
91. player1 ! Zong(player2)
92.  
93. player1 ! Ping(player2)
94.  
95. player1 ! Zong(player2)
96.  
97. actorSystem.shutdown
98.  
99.  
100.  
101. /********************* POISON_PILL *********************
102.  
103.  * A PoisonPill message will stop an actor when the message is processed.
104.  
105.  * A PoisonPill message is queued just like an ordinary message
106.  
107.  * and will be handled after other messages queued ahead of it in its mailbox.
108.  
109.  */
110.  
111.  
112.  
113. /********************* context.stop(self) *********************
114.  
115.  * The difference is in which messages get processed before this sequence starts.
116.  
117.  * In the case of the stop call, the message currently being processed is completed first,
118.  
119.  * with all others discarded.
120.  
121.  */
122.  
123.  
124.  
125. /********************* Console output *********************
126.  
127.  * scala> :load 12_1.scala
128.  
129.  * Loading 12_1.scala...
130.  
131.  * import akka.actor._
132.  
133.  * defined class Ping
134.  
135.  * defined class Pong
136.  
137.  * defined class Zong
138.  
139.  * defined class Player
140.  
141.  * NUMBER_OF_RALLIES: Int = 5
142.  
143.  * actorSystem: akka.actor.ActorSystem = akka://PingPongTraining
144.  
145.  * player1: akka.actor.ActorRef = Actor[akka://PingPongTraining/user/$a#-1157019602]
146.  
147.  * player2: akka.actor.ActorRef = Actor[akka://PingPongTraining/user/$b#-546795948]
148.  
149.  * Unhandled message
150.  
151.  * ping
152.  
153.  * pong
154.  
155.  * ping
156.  
157.  * pong
158.  
159.  * ping
160.  
161.  * pong
162.  
163.  * ping
164.  
165.  * pong
166.  
167.  * ping
168.  
169.  * pong
170.  
171.  * [INFO] [01/15/2018 22:07:07.545] [PingPongTraining-akka.actor.default-dispatcher-5] [akka://PingPongTraining/user/$a] Message [$line233.$read$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$Zong] from Actor[akka://PingPongTraining/deadLetters] to Actor[akka://PingPongTraining/user/$a#-1157019602] was not delivered. [1] dead letters encountered. This logging can be turned off or adjusted with configuration settings 'akka.log-dead-letters' and 'akka.log-dead-letters-during-shutdown'.
172.  
173.  *  */