(* a simple echo server in ocaml 
 * -----------------------------
 * uses a high level networking function, similar to SocketServer
 * in python, called 'establish_server', see here:
 * http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#VALestablish_server
 *)
 
(* 
  our echo function 
  in -> out -> unit 
*)
let echo ic oc =let echo ic oc =
  let c = ref true in
  while !c do
    let pid  = Unix.getpid () in
    let msg  = Printf.sprintf "[%d] echo> " pid in
      output oc msg 0 (String.length msg);
      flush oc;
      let l = try input_line ic with End_of_file -> c := false; "" in
      let resp = Printf.sprintf "[%d] echo'd> %s\n" pid l in
        output oc resp 0 (String.length resp)
  done
 
 
 
(* main *)
let _ =
  let addr = Unix.inet_addr_of_string "0.0.0.0" in (* localhost *)
  let sa   = Unix.ADDR_INET (addr,4242) in         
 
  (* (in -> out -> unit) -> sockaddr -> () *)
  Unix.establish_server echo sa