GenServer

defmodule MyServer do
  
  def ack(conn, frame) do
    GenServer.cast(conn, { :acknowledge, frame })
  end
  
  def register_callback(conn, destination, callback) do
    GenServer.call(conn, { :register_callback, destination, callback })
  end
  
  def handle_cast({ :acknowledge, frame }, %{ sock: sock } = state) do
    ack_frame = FB.build_frame("ACK", %{
      id: frame.headers["message-id"]
    })

    FH.send_frame(sock, ack_frame)
    { :noreply, state }
  end
  
  def handle_info({ :tcp, _, data}, %{ sock: sock, callbacks: callbacks } = state) do
    frame = FH.parse_frame(data)
    destination = frame.headers["destination"]

    Dict.get(callbacks, destination, [])
    |> Enum.map(fn(func) -> func.(frame) end)

    :inet.setopts(sock, active: :once)
    { :noreply, state }
  end

end

gistfile1.txt

test = fn (msg)-> 
  IO.puts "HELLO" 
  MyServer.ack(conn, msg)
end

MyServer.register_callback conn, "/queue/testing", test