ScalaのAdvanced Exampleを写経する(8)-socket

Javaのソケット通信を使ったクライアント/サーバーアプリ。
random.scala | The Scala Programming Language

package sample.snippet

import java.io._
import java.net.{ InetAddress, ServerSocket, Socket, SocketException }
import java.util.Random

/** Simple client/server application using Java sockets.
 * 
 * The server simply generates random integer values
 * and the clients provide a filter function to the server
 * to get only values they interested in (eg. even or odd values, and so on).
 */
object randomclient {

  def main(args: Array[String]) {
    val filter: Int => Boolean = try {
      Integer.parseInt(args(0)) match {
        case 1 => x: Int => x % 2 != 0
        case 2 => x: Int => x % 2 == 0
        case _ => x: Int => x != 0
      }
    } 
    catch {
      case _ => x: Int => x < 100
    }
    
    try {
      val ia = InetAddress.getByName("localhost")
      val socket = new Socket(ia, 9999)
      val out = new ObjectOutputStream (
        new DataOutputStream(socket.getOutputStream))
      val in = new DataInputStream(socket.getInputStream())
      
      out.writeObject(filter)
      out.flush()
      
      while (true) {
        val x = in.readInt()
        println("x = " + x) 
      }
      out.close
      in.close
      socket.close
    } 
    catch {
      case e: IOException => e.printStackTrace()
    } 
  }
  
  case class ServerThread(socket: Socket) extends Thread("ServerThread") {
    override def run(): Unit = {
      val rand = new Random(System.currentTimeMillis)
      try {
        val out = new DataOutputStream(socket.getOutputStream)
        val in = new ObjectInputStream(
          new DataInputStream(socket.getInputStream))
        
        val filter = in.readObject.asInstanceOf[Int => Boolean]
        
        while (true) {
          var succeeded = false
          do {
            val x = rand.nextInt(1000)
            succeeded = filter(x)
            if (succeeded) out.writeInt(x)
          } while (! succeeded);
          Thread.sleep(100)
        }
      }
      catch {
        case e: SocketException =>
          () // aviod stack trace when stopping a client with Ctrl-C
        case e: IOException =>
            e.printStackTrace
      }
    }
  }  
}
  object randomserver {
    def main(args: Array[String]): Unit = {
      import randomclient._
      try {
        val listener = new ServerSocket(9999)
        while (true) {
          new ServerThread(listener.accept()).start()
        }
        listener.close()
      }
      catch{
        case e: IOException =>
          System.err.println("Could not listen op port: 9999.")
          System.exit(-1)
      }
    }
  }

特に問題なしかな。
パターンマッチングにおける「_」はどれにも当てはまらなかった場合のデフォルト。
JavaのInetAddressクラスなんて知らなかった。JDK1.0からあるんだね。

実行結果。

x = 49
x = 80
x = 53
x = 4
x = 22
x = 59
x = 62
x = 47
x = 41
x = 39
x = 68
x = 49
x = 52
x = 30
x = 63