This small scala example demonstrates the simplicity in which distributed programming is possible using the actor model. We setup an ECHOSERVER that simply responds with a PONG to any PING request it receives and we run this on an arbitrary server.

/*
 * EchoServer.scala
 */
 
package echoapp
 
import scala.actors.Actor._
import scala.actors.remote.{Locator,Node,RemoteActor}
import scala.actors.remote.RemoteActor.{alive,register}
 
class Server(me : Locator) {
    RemoteActor.classLoader = getClass().getClassLoader()
    actor {
        alive(me.node.port)
        register(me.name, self)
        loop {
            react {
                case 'PING => reply("PONG") // equiv:  sender ! "PONG"
                case msg => println(msg)
            }
        }
    }
}
 
object EchoServer  {
    def main(args: Array[String]) {
        val me = new Locator(Node("127.0.0.1", 9010), 'echoServer)
        new Server(me)
        println("Echo server started")
    }
}

For the sake of brevity the IP address of where the ECHOSERVER is running has been hardcoded. The client sends a PING message to the remote echo server and gathers the response(s).

/*
 * EchoClient.scala
 */
 
package echoapp
 
import scala.actors.Actor._
import scala.actors.remote.{Locator,Node,RemoteActor}
import scala.actors.remote.RemoteActor._
 
class Client(servloc : Locator) {
    RemoteActor.classLoader = getClass().getClassLoader()
    val server = select(servloc.node, servloc.name)
    actor {
        // The response is sent back to the thread that did the send.
        // If we move to this to main() then this is where the reponse will go
        // as we have no react/receive there it will be lost.
        server ! 'PING
        loop {
            react {
                case msg => 
                    println(msg)
            }
        }
    }    
}
 
object EchoClient {
    def main(args: Array[String]) {
        val echoServer = Locator(Node("192.168.1.13", 9010), 'echoServer)
        new Client(echoServer)
    }
}