akka-http + akka-atreamでWebSocketサーバを実装

build.sbt

name := "websocket-server"

version := "0.1.0"

scalaVersion := "2.11.7"

libraryDependencies ++= Seq(
  "com.typesafe.akka" % "akka-stream-experimental_2.11"    % "2.0-M2",
  "com.typesafe.akka" % "akka-http-core-experimental_2.11" % "2.0-M2",
  "com.typesafe.akka" % "akka-http-experimental_2.11"      % "2.0-M2"
)

Main.scala

import akka.actor.ActorSystem
import akka.stream.ActorMaterializer
import akka.stream.scaladsl._
import akka.http.scaladsl.Http
import akka.http.scaladsl.model._
import akka.http.scaladsl.model.ws._
import akka.http.scaladsl.model.HttpMethods._

import scala.concurrent.Await
import scala.concurrent.duration.Duration

object Main extends App {
  implicit val system = ActorSystem("websocket-server")
  implicit val materializer = ActorMaterializer()

  val echoFlow: Flow[Message, Message, Unit] = Flow[Message].mapConcat {
    case tm: TextMessage => TextMessage(tm.textStream) :: Nil
    case _ => Nil
  }

  val requestHandler: HttpRequest => HttpResponse = {
    case req @ HttpRequest(GET, Uri.Path("/"), _, _, _) =>
      req.header[UpgradeToWebsocket] match {
        case Some(upgrade) => upgrade.handleMessages(echoFlow)
        case None => HttpResponse(400)
      }
    case _: HttpRequest => HttpResponse(400)
  }

  val binding = Http().bindAndHandleSync(requestHandler, interface = "localhost", port = 8080)

  Await.ready(binding, Duration.Inf)
}