WebSocket Client and Server

Client.scala

import akka.Done
import akka.actor.ActorSystem
import akka.http.scaladsl.Http
import akka.http.scaladsl.model.StatusCodes
import akka.http.scaladsl.model.ws.TextMessage.Strict
import akka.http.scaladsl.model.ws.{Message, TextMessage, WebSocketRequest}
import akka.stream.scaladsl.{Flow, Keep, Sink, Source, SourceQueue}
import akka.stream.{ActorMaterializer, OverflowStrategy}

import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.Future
import scala.concurrent.duration._

object TestClient extends App {

  implicit val system = ActorSystem()
  implicit val materializer = ActorMaterializer()

  case class MessageOffering(queue: SourceQueue[TextMessage.Strict]) {
    def offerMessage: Unit = {
      queue.offer(TextMessage("Bang!"))
    }
  }

  val queue: Source[TextMessage.Strict, SourceQueue[TextMessage.Strict]] = Source.queue[TextMessage.Strict](10, OverflowStrategy.dropNew)
  val queueSource = queue.mapMaterializedValue { (queue: SourceQueue[Strict]) =>
    val messageOfferer = MessageOffering(queue)
    system.scheduler.schedule(5.seconds, 1.second) { messageOfferer.offerMessage }
  }

  val sink: Sink[Message, Future[Done]] = Sink.foreach {
    case message: TextMessage.Strict => println(message.text)
    case _ =>
  }

  val flow: Flow[Message, Message, Future[Done]] = Flow.fromSinkAndSourceMat(sink, queueSource)(Keep.left)

  val (upgradeResponse, closed) = Http().singleWebSocketRequest(WebSocketRequest("ws://localhost:8080"), flow)

  val connected = upgradeResponse.map { upgrade =>
    if (upgrade.response.status == StatusCodes.SwitchingProtocols) {
      Done
    } else {
      throw new RuntimeException("Connection failed!")
    }
  }

  connected.onComplete(println)
  closed.foreach(_ => println(closed))
}

Server.js

const WebSocket = require('ws');

const wss = new WebSocket.Server({
  port: 8080
});

console.log('Running!');

wss.on('connection', function connection(ws) {
  ws.send('welcome aboard');
  console.log("Connection established!");

  ws.on('message', function incoming(data, flags) {
    console.log(data);
    ws.send('hi there!');
  });
});