how to get websocket working with play and Concurrent.broadcast - scala

Question

Here is what the document recommends and it does work.
import play.api.mvc._
import play.api.libs.iteratee._
import play.api.libs.concurrent.Execution.Implicits.defaultContext
def socket = WebSocket.using[String] { request =>
// Concurrent.broadcast returns (Enumerator, Concurrent.Channel)
val (out, channel) = Concurrent.broadcast[String]
// log the message to stdout and send response back to client
val in = Iteratee.foreach[String] {
msg => println(msg)
// the Enumerator returned by Concurrent.broadcast subscribes to the channel and will
// receive the pushed messages
channel push("I received your message: " + msg)
}
(in,out)
}
However it is not working if I changed to:
def socket = WebSocket.using[String] { request =>
val (out, channel) = Concurrent.broadcast[String]
val in=Iteratee.ignore[String]
channel push("Hello World")
(in,out)
}
I'd appreciate if you can help me understand why it is not working with the new approach.
Thanks
James
Update:
class ServiceHandler extends Actor {
import Tcp._
val (enumerator, channel) = Concurrent.broadcast[String]
val system=ActorDict.system
def receive = {
case subscribeData() =>{
sender ! enumerator
}
case Received(data) => {
val dst = data.decodeString("utf-8")
val va=dst.substring(dst.lastIndexOf(',') + 1).trim()
println(va)
channel.push(va)
}
case PeerClosed => context stop self
}
}
def ws = WebSocket.using[String] { request =>
val in=Iteratee.ignore[String]
val dataHandler = Akka.system.actorOf(Props[ServiceHandler])
val out= Await.result((dataHandler ? subscribeData()), 5 seconds).asInstanceOf[Enumerator[String]]
(in,out)
}

Answer 1

You will not receive the "hello world" in the client side because you're pushing it to the channel before the connection is established with the client.
If you don't need to receive anything from the client ( this is why you're doing val in=Iteratee.ignore[String] ) You'd better go with server sent events:
Ok.chunked(out &> EventSource()).as("text/event-stream")