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

[Raphael Bauduin <rblists@gmail.com>]

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Thanks for your answer!

I get the same result with the following code. Note that I can open 2
connections and that the closing of the connection works as expected with a
'close connection' pattern (with one line only with a dot followed by an
empty line). It is just that I cannot close the second connection while the
first stays open, the 'close connection' pattern is not triggering the
close.

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
let server port =
  let inet_addr = inet_addr_any in
  let sockaddr = ADDR_INET (inet_addr, port) in
  let domain = domain_of_sockaddr sockaddr in
  let sock:Unix.file_descr = socket domain SOCK_STREAM 0 in
  Unix.bind sock sockaddr;
  listen sock 10;
  Lwt_main.run ( Lwt.return (accept_connection sock) )


On Sun, Nov 27, 2016 at 6:41 PM, Koen De Keyser <koen.dekeyser@gmail.com>
wrote:

> 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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