Scala example source code file (SocketServer.scala)

This example Scala source code file (SocketServer.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

accept, boolean, compile, compileoutputcommon, compiler, left, nsc, serversocket, socketexception, socketserver, string, unit

The SocketServer.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2002-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala
package tools.util

import java.net.{ ServerSocket, SocketException, SocketTimeoutException }
import java.io.{ PrintWriter, BufferedReader }
import scala.tools.nsc.io.Socket

trait CompileOutputCommon {
  def verbose: Boolean

  def info(msg: String)  = if (verbose) echo(msg)
  def echo(msg: String)  = {Console println msg; Console.flush()}
  def warn(msg: String)  = {Console.err println msg; Console.flush()}
  def fatal(msg: String) = { warn(msg) ; sys.exit(1) }
}

/** The abstract class SocketServer implements the server
 *  communication for the fast Scala compiler.
 *
 *  @author  Martin Odersky
 *  @version 1.0
 */
abstract class SocketServer extends CompileOutputCommon {
  def shutdown: Boolean
  def session(): Unit
  def timeout(): Unit = ()  // called after a timeout is detected for subclasses to cleanup
  // a hook for subclasses
  protected def createServerSocket(): ServerSocket = new ServerSocket(0)

  var in: BufferedReader = _
  var out: PrintWriter   = _
  val BufferSize         = 10240
  lazy val serverSocket  = createServerSocket()
  lazy val port          = serverSocket.getLocalPort()

  // Default to 30 minute idle timeout, settable with -max-idle
  protected var idleMinutes = 30
  private var savedTimeout = 0
  private val acceptBox = new Socket.Box(() => {
    // update the timeout if it has changed
    if (savedTimeout != idleMinutes) {
      savedTimeout = idleMinutes
      setTimeoutOnSocket(savedTimeout)
    }
    new Socket(serverSocket.accept())
  })
  private def setTimeoutOnSocket(mins: Int) = {
    try {
      serverSocket setSoTimeout (mins * 60 * 1000)
      info("Set socket timeout to " + mins + " minutes.")
      true
    }
    catch {
      case ex: SocketException =>
        warn("Failed to set socket timeout: " + ex)
        false
    }
  }

  def doSession(clientSocket: Socket) = {
    clientSocket.applyReaderAndWriter { (in, out) =>
      this.in    = in
      this.out   = out
      val bufout = clientSocket.bufferedOutput(BufferSize)

      try scala.Console.withOut(bufout)(session())
      finally bufout.close()
    }
  }

  def run() {
    info("Starting SocketServer run() loop.")

    def loop() {
      acceptBox.either match {
        case Right(clientSocket) =>
          try doSession(clientSocket)
          finally clientSocket.close()
        case Left(_: SocketTimeoutException) =>
          warn("Idle timeout exceeded on port %d; exiting" format port)
          timeout()
          return
        case _ =>
          warn("Accept on port %d failed")
      }
      if (!shutdown)
        loop()
    }
    try loop()
    catch { case ex: SocketException => fatal("Compile server caught fatal exception: " + ex) }
    finally serverSocket.close()
  }
}