How to open TCP connection with TLS in scala using akka

Question

I want to write a Scala client that talks a proprietary protocol over a tcp connection with TLS.

Basically, I want to rewrite the following code from Node.js in Sca

Answer 1

I really liked Jeremias Werner's answer as it got me where I needed to be. However, I would like to offer the code below (heavily influenced by his answer) as a "one cut and paste" solution that hits an actual TLS server using as little code as I had time to produce.

import javax.net.ssl.SSLContext

import akka.NotUsed
import akka.actor.ActorSystem
import akka.stream.TLSProtocol.NegotiateNewSession
import akka.stream.scaladsl.{BidiFlow, Flow, Sink, Source, TLS, Tcp}
import akka.stream.{ActorMaterializer, OverflowStrategy, TLSProtocol, TLSRole}
import akka.util.ByteString

object TlsClient {

  // Flow needed for TLS as well as mapping the TLS engine's flow to ByteStrings
  def tlsClientLayer = {

    // Default SSL context supporting most protocols and ciphers. Embellish this as you need
    // by constructing your own SSLContext and NegotiateNewSession instances.
    val tls = TLS(SSLContext.getDefault, NegotiateNewSession.withDefaults, TLSRole.client)

    // Maps the TLS stream to a ByteString
    val tlsSupport = BidiFlow.fromFlows(
      Flow[ByteString].map(TLSProtocol.SendBytes),
      Flow[TLSProtocol.SslTlsInbound].collect {
        case TLSProtocol.SessionBytes(_, sb) => ByteString.fromByteBuffer(sb.asByteBuffer)
      })

    tlsSupport.atop(tls)
  }

  // Very simple logger
  def logging: BidiFlow[ByteString, ByteString, ByteString, ByteString, NotUsed] = {

    // function that takes a string, prints it with some fixed prefix in front and returns the string again
    def logger(prefix: String) = (chunk: ByteString) => {
      println(prefix + chunk.utf8String)
      chunk
    }

    val inputLogger = logger("> ")
    val outputLogger = logger("< ")

    // create BidiFlow with a separate logger function for each of both streams
    BidiFlow.fromFunctions(outputLogger, inputLogger)
  }

  def main(args: Array[String]): Unit = {
    implicit val system: ActorSystem = ActorSystem("sip-client")
    implicit val materializer: ActorMaterializer = ActorMaterializer()

    val source = Source.actorRef(1000, OverflowStrategy.fail)
    val connection = Tcp().outgoingConnection("www.google.com", 443)
    val tlsFlow = tlsClientLayer.join(connection)
    val srcActor = tlsFlow.join(logging).to(Sink.ignore).runWith(source)

    // I show HTTP here but send/receive your protocol over this actor
    // Should respond with a 302 (Found) and a small explanatory HTML message
    srcActor ! ByteString("GET / HTTP/1.1\r\nHost: www.google.com\r\n\r\n")
  }
}