An example on how to use an EventStream in Akka. See article http://danielasfregola.com/2015/04/20/peer-to-many-communication-in-akka/

Events.scala

package com.eventstream
import java.util.Date

/**
 * Created by prayagupd
 * on 2/6/16.
 */

trait Event
trait MessageLog

case class PackageArrivedEvent(packageId: String, items: List[String]) extends Event
case class PackageShipped(shippedDate: Date) extends MessageLog

EventStreamApplication.scala

import akka.actor._
import com.eventstream.PackageArrivedEvent
import com.eventstream.publisher.PackageArrivedPublisher
import com.eventstream.subscriber.PackageArrivedSubscriber

object EventStreamApplication extends App {

  implicit val system = ActorSystem("event-stream")

  val packageId = "package001"

  val packagePublisher = system.actorOf(Props[PackageArrivedPublisher], name = "package-publisher")

  val subscriber1 = system.actorOf(Props[PackageArrivedSubscriber], name = "subscriber-1")
  val subscriber2 = system.actorOf(Props[PackageArrivedSubscriber], name = "subscriber-2")

  packagePublisher ! PackageArrivedEvent(packageId = "package001", items = List("shirts", "pants"))

  system.eventStream.unsubscribe(subscriber2, classOf[PackageArrivedEvent])

  packagePublisher ! PackageArrivedEvent(packageId = "package002", items = List("underwear"))
}

PackageArrivedPublisher.scala

package com.eventstream.publisher

import akka.actor._
import com.eventstream.PackageArrivedEvent

/**
 * Created by prayagupd
 * on 2/7/16.
 */

class PackageArrivedPublisher extends Actor {
  def receive = {
    case packageToShip: PackageArrivedEvent => {
      println(s"Publishing a new package - $packageToShip")
      context.system.eventStream.publish(packageToShip)
    }
  }
}

PackageArrivedSubscriber.scala

package com.eventstream.subscriber

import akka.actor.Actor
import com.eventstream.PackageArrivedEvent
/**
 * Created by prayagupd
 * on 2/7/16.
 */

class PackageArrivedSubscriber extends Actor {

  override def preStart =
    context.system.eventStream.subscribe(self, classOf[PackageArrivedEvent])

  def receive = {
    case packageToShip: PackageArrivedEvent =>
      println(s"${self.path.name} - receiving a new package: $packageToShip")
  }
}