Re: [Caml-list] Beginner's question on Lwt usage

[Koen De Keyser <koen.dekeyser@gmail.com>]

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You need to run your lwt code within Lwt_main.run

This starts the lwt scheduler. Otherwise your application just terminates
once it has created the lwt thread (which is a simple Ocaml value).

Koen

On Nov 27, 2016 18:30, "Raphael Bauduin" <rblists@gmail.com> wrote:

> Hi,
>
> After writing a small tcp server in ocaml, I wanted to make it work
> asynchronously with Lwt.
> I changed the function handling the accept on the socket to look like this:
>
> let rec accept_connection sock:Unix.file_descr =
>   let socket_thread = Lwt.return ( Unix.accept sock ) in
>   let _ = Lwt.bind socket_thread
>          ( fun (fd, caller) ->
>              ignore(Lwt_io.printf "accepted\n%!");
>              (*let _ = set_nonblock fd in*)
>              Lwt.return (readall fd) >>= fun a ->
>                  ignore(Lwt_io.printf "%s\n%!" a);
>                  ignore(Lwt.async (fun () -> Lwt.return (close fd) ) );
>                  Lwt.return 0;
>          ); in
>    accept_connection sock
>
> The complete code is at http://pastie.org/10971189 .
>
> But it doesn't seem to work. The problems are:
> - nothing is printed on stdout
> - when I open 2 connections, the second can only be closed after the first
> has been closed.
>
> In the mean time I've discovered Lwt_unix, but before looking at it, I'd
> like to understand what's wrong in my current code. Can you spot errors in
> the code? General advice is also welcome!
>
> Thanks
>
> Raphael
>
>
>

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