Ah, now I read your code in more detail I think I see why.

Reader.contents on the server side will block until eof. The client side sends some stuff, but does not close the writer, so the server never sees eof. (Recall that sockets are not like files: it's possible to read all of the available data right now, but not reach eof.)

Network protocols normally have some explicit "this is the end of one message" marker, like a newline or something similar. Then the server just reads chunks until it sees that marker, at which point it can put the message together and to something with it.

For example, you could use Writer.write_line on the client side and Reader.read_line on the server side.

On 16 June 2015 at 16:36, Kenneth Adam Miller <kennethadammiller@gmail.com> wrote:
So, now I can get server received if I add that into the callback, but at "writing shutdown to server" I don't see response received or even something for Eof.

On Tue, Jun 16, 2015 at 11:09 AM, David House <dhouse@janestreet.com> wrote:
The first thing to try is to make sure that everything is getting flushed. For temporary debugging messages I strongly recommend just using [Core.Std.eprintf "<message>\n%!"].

On 16 June 2015 at 16:03, Kenneth Adam Miller <kennethadammiller@gmail.com> wrote:
I'm having trouble with OCaml Async. I wrote a small server with it, and right now I'm trying to unit test that server. Here's my code for the server:


let _main ()=
  print_endline "Server running";
  let handler = print_endline in
  let socket = Tcp.on_port 5554 in
  let server = Tcp.Server.create socket (fun addr r w ->
      (Reader.contents r) >>| handler; (Writer.write w "got it")) in
  server



In my unit test code I have:

let test_shutdown test_ctxt = Thread_safe.block_on_async_exn (fun () -> (
      print_endline "test_shutdown";
      let server = Server._main () in
      server >>= fun server ->
      let where = Tcp.to_host_and_port "127.0.0.1" 5554 in
      Tcp.connect where >>= fun s -> 
        let socket, r, w = s in
        ignore (Writer.write w "kill");
        ignore (Writer.flushed w);
        (Reader.recv r >>> function
          | `Ok result ->  print_endline ("writing shutdown to server" ^ result)
          | `Eof -> ());
        return ()
    )); ()



I see test_shutdown and Server running, but not sign of "writing shutdown to server" or even "got it"; why isn't my server or even any of the connection executing?