Client/server communication over unix domain sockets - Ocaml

(* ocamlfind ocamlc unixsocket.ml -package unix -linkpkg && ./a.out *)
(* Example of 2 ocaml programs communicating over a UNIX socket. *)

let socket_file = "domotique.sock";;

(* Remove the file if it already existed. *)
try Unix.unlink socket_file with Unix.Unix_error _ -> ();;

module Server() = struct
  let socket = Unix.socket Unix.PF_UNIX Unix.SOCK_STREAM 0;;

  (* Remove the file after it was created. *)
  Pervasives.at_exit (fun () ->
    Unix.unlink socket_file
  );;

  Unix.bind socket (Unix.ADDR_UNIX socket_file);;
  Unix.listen socket 1;;

  Printf.printf "After listen \n%!";;

  let client_sock, _ = Unix.accept socket;;

  (* We assume that we only have a single client for now. *)

  Printf.printf "Client found \n%!";;

  let in_chan = Unix.in_channel_of_descr client_sock;;
  let out_chan = Unix.out_channel_of_descr client_sock;;
  let res:string = Marshal.from_channel in_chan;;
  Printf.printf "Client send: %s\n%!" res;;


  Marshal.to_channel out_chan "Hello, client!" [];;
  Pervasives.flush out_chan;

end

module Client()= struct

    Unix.sleep 1;;                (* Wait for the server to create the socket. *)

  (* Low-level version. *)
  let socket = Unix.socket Unix.PF_UNIX Unix.SOCK_STREAM 0;;
  Unix.connect socket (Unix.ADDR_UNIX socket_file);;
  let in_chan = Unix.in_channel_of_descr socket;;
  let out_chan = Unix.out_channel_of_descr socket;;

  (* High-level version. *)
  (* let in_chan,out_chan = Unix.open_connection (Unix.ADDR_UNIX socket_file);; *)

  Marshal.to_channel out_chan "Hello, server!" [];;
  Pervasives.flush out_chan;
  let result = Marshal.from_channel in_chan in
  Printf.printf "Server answered: %s\n%!" result;;

end;;

match Unix.fork() with
| 0 -> let module C = Client() in ()
| _ -> let module S = Server() in ()
;;