Send stdin lines to websocket and dump (asynchronously) everything coming from the websocket to stdout / published by https://github.com/dacr/code-examples-manager #57415e71-093a-4470-8c09-e80426ddd438/f25bebeda8fad5cdd2137e00d264b1751d604f92

akka-wscat.sc

// summary : Send stdin lines to websocket and dump (asynchronously) everything coming from the websocket to stdout
// keywords : scala, actors, akka, http-client, client, websocket, cat
// publish : gist
// authors : David Crosson
// license : Apache NON-AI License Version 2.0 (https://raw.githubusercontent.com/non-ai-licenses/non-ai-licenses/main/NON-AI-APACHE2)
// id : 57415e71-093a-4470-8c09-e80426ddd438
// created-on : 2021-02-05T18:06:03Z
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : scala-cli $file
// usage-example : scala-cli akka-wscat.sc -- ws://127.0.0.1:8080

// ---------------------
//> using scala  "2.13.11"
//> using objectWrapper
//> using dep "com.typesafe.akka::akka-http:10.2.10"
//> using dep "com.typesafe.akka::akka-stream-typed:2.6.21"
//> using dep "com.typesafe.akka::akka-actor-typed:2.6.21"
////> using dep "org.slf4j:slf4j-nop:2.0.7"
//> using dep "org.slf4j:slf4j-simple:2.0.7"
// ---------------------

import akka.actor.typed.{ActorRef, Behavior}
import akka.actor.typed.scaladsl.Behaviors
import akka.Done

import akka.stream.scaladsl._
import akka.stream._
import akka.stream.typed.scaladsl.ActorSource

import akka.http.scaladsl._
import akka.http.scaladsl.model.StatusCodes
import akka.http.scaladsl.model.ws.{BinaryMessage, Message, TextMessage, WebSocketRequest}

import scala.annotation.tailrec
import scala.concurrent._
import scala.concurrent.duration._
import scala.io.StdIn


object Protocol {
  // -------------------------------------------------------------------------------------------
  // Actor behavior to manage input data
  sealed trait Send
  case class SendRegister(controlActorRef: ActorRef[Control]) extends Send
  case class SendTransmit(content: String) extends Send
  object SendFinished extends Send

  def behaviorSend(): Behavior[Send] = Behaviors.receiveMessage {
    case SendRegister(controlActorRef) =>
      Behaviors.receiveMessage {
        case SendTransmit(content) =>
          controlActorRef ! ControlContent(content)
          Behaviors.same
        case SendFinished =>
          controlActorRef ! ControlDone
          Behaviors.stopped // Means shutdown the actor system here !
      }
  }

  // -------------------------------------------------------------------------------------------
  // To talk with the created Source actor
  sealed trait Control
  object ControlDone extends Control
  case class ControlContent(content:String) extends Control
  case class ControlFailure(ex:Exception) extends Control
}


val onlineWebSocketEchoServices = List(
  "wss://demo.piesocket.com",
  //"wss://socketsbay.com/wss/v2/1/demo/", // no echo response :(
  //"ws://echo.websocket.org" // decommissioned on 2021 !
)


import Protocol._
implicit val system = akka.actor.typed.ActorSystem[Send](behaviorSend(), "MySystem")
implicit val executionContext = system.executionContext

val uri = args.headOption.getOrElse(onlineWebSocketEchoServices.head)

// bufferSize & overflowStrategy are important to deal with fast input rate
// With stdIn no backpressure is possible I guess
val (controlActorRef, outgoing) =
  ActorSource.actorRef[Control](
    completionMatcher = {case ControlDone => },
    failureMatcher = {case ControlFailure(ex) => ex},
    bufferSize=10000,
    overflowStrategy = OverflowStrategy.dropNew
  ).preMaterialize()


system ! SendRegister(controlActorRef)

val incoming: Sink[Message, Future[Done]] =
  Sink.foreach[Message] {
    case TextMessage.Strict(text) =>
      println(text)
    case TextMessage.Streamed(stream) =>
      val text = stream.runReduce(_ + _) // Force consume and concat all responses fragments
      text.map(System.out.println).andThen(_ => System.out.flush) // TODO better handling of this future ?
    case BinaryMessage.Strict(bin) =>
      println("Strict binary message not supported ")
    case BinaryMessage.Streamed(bin) =>
      println("Streamed binary message not supported ")
      bin.runWith(Sink.ignore)  // Force consume (to free input stream)
    case x =>
      println(s"Not understood entry $x")
  }

println(s"Request websocket from $uri")
val flow = Http().webSocketClientFlow(request = WebSocketRequest(uri = uri))

val (upgradedResponse, closed) =
  outgoing
    .map{case ControlContent(content) => TextMessage(content) }
    .viaMat(flow)(Keep.right)
    .toMat(incoming)(Keep.both)
    .run()

val connected = upgradedResponse.flatMap { upgrade =>
  if (upgrade.response.status == StatusCodes.SwitchingProtocols) {
    Future.successful(Done)
  } else {
    throw new RuntimeException(s"Connection failed: ${upgrade.response.status}")
  }
}

@tailrec
def loop(): Unit = {
  val input = Option(StdIn.readLine()) // returns null for EOF so NONE in our case
  input match {
    case Some(content) =>
      system ! SendTransmit(content+"\n")
      loop()
    case None => system ! SendFinished
  }
}

new Thread() {
  override def run(): Unit = {
    loop()
  }
}.start()