使用Akka IO在Tcp客户端上发送非ByteString

Question

I am using akka-io to create a Tcp Client Actor that communicates with a non-jvm tcp (non-akka) server over a socket. Because akka-io sends ByteString and the program expects a regular String outputted to it, the ByteString message is never processed. A very crude java based approach to this actually works :

override def receive: Receive = {
    case ClientTcpActor.Start =>
      val socket = new Socket(socketAddress.getHostName, socketAddress.getPort)
      val out = new PrintWriter(socket.getOutputStream, true)
      out.println("Hello World!")
      import java.io.BufferedReader
      import java.io.InputStreamReader
      val is = socket.getInputStream
      val isr = new InputStreamReader(is)
      val br = new BufferedReader(isr)
      val message = br.readLine
      println(s"Message received from the server : $message")
}

I am able to send a message to the tcp port and receive a response back.

However, this akka-io approach doesnt work. Specifically, I never receive data back from the socket because the external application cant process the ByteString sent by the Write object

def receive: PartialFunction[Any, Unit] = {
    case CommandFailed(_: Connect) =>
      log.info("Connection failed.")
      context stop self

    case c@Connected(_, _) =>
      log.info("Connect succeeded.")
      val connection = sender()
      connection ! Register(self)
      val message = ByteString("hello world")
      log.info(s"Sending request message ${message}")
      connection ! Write(message)

    case Received(data) =>
      log.info(data.toString())


    case _: ConnectionClosed =>
      log.info("Connected is closed!")
    case _ =>
      log.info("Something else is up.")
  }

I also created my own akka-IO server application that processes data on the same port and verified that I was actually sending the message to the port, but the akka server actor was needed to process the decoding of the ByteString

Im hoping this is some easy-fix I'm overlooking.

Answer 1

Over the network there is no such thing as String or ByteString , there are only bytes. ByteString is essentially just a wrapper around byte arrays to ensure they are not mutated (as that would then require synchronisation for it to be safe to share between threads/actors). When you create a ByteString from a String it will use an encoding ( UTF8 in this case) to encode the string into bytes.

Can't say what is wrong from the pieces of your code that you included, but there is a complete example client in the docs that may be helpful to compare your code to: http://doc.akka.io/docs/akka/current/scala/io-tcp.html#Connecting