Finnagle Error running client/server in same JVM

Question

I´m having a very bizzare behaviour with Twitter finagle client/server.

Having a Server

  def start(): Unit = {
    val port=8500
    println(s"Running Finagle Mock Server in port $port.......")
    mockServer = Some(Http.server
      .configuredParams(finagle.Http.Http2)
      .configured(finagle.Http.Netty4Impl)
      .serve(s"localhost:$port", mockService))
  }

And a client

  override def client():Unit = {
    val clientService = Http.newService("localhost:8500")
    val future: Future[Response] = clientService(createRequestUsingBuilderWithJson())
    future.onFailure(th =>{
      println(th)
    })
    future.onSuccess(value => {
      println(value)
    })
    val response: Response = Await.result(future)
    println(response.contentString)
  }

  @throws[Exception]
  def createRequestUsingBuilderWithJson(): Request = {
    new RichHttpRequestBuilder()
     .withMethod(Method.Get).withPath("/rest_connection/external_service").build
  }

If I run the server as an App in another JVM process and then I run the client everything is fine, I can reach the server and a 200 response is received.

But if instead of run first in another process the server I run in the samr JVM before run ther client the communication never reach the server and I just receive in my onFailure client callback

DefaultHttpResponse(chunked: false)
HTTP/1.1 500 Internal Server Error
content-length: 0
Connection: close

Any idea why I cannot run client/server in the same JVM???