Creating a Chat Server

Question

I am creating a chat server in the Ocaml language using lwt. What I want it to be able to do is prompt the user to enter a nickname, store the nickname, and then output that the user has joined the chat.

I have already tried implementing my own code, as shown below.

let sessions = ref [("",Lwt_io.null)]

(*  + obtain initial nick(name),
    + add (nick,outp) to !sessions, and
    + announce join to other users *)
let handle_login nr (inp,outp) =
  Lwt_io.printl "Enter initial nick:" >>= (* Print a welcome message to outp *)
  fun () -> Lwt_io.read_line inp >>= (* Read the user's nick from inp *)
  fun s -> Lwt.return (nr := s); (* Assign the new value to nr *)
  sessions := List.concat nr (* Adds nr to sessions *)
  send_all nr "<joined>" >>= (* Inform the other users that the user joined *)
  fun () -> Lwt.return ()

let rec send_all sender msg = Lwt.return ()

let chat_server _ (inp,outp) =
  let nick = ref "" in
  let _ = handle_login nick in (* Calls handle_login with nick *)
  let rec main_loop () =
      Lwt_io.read_line inp >>= handle_input nick outp >>= main_loop in
  Lwt.catch main_loop (fun e -> handle_error e !nick inp outp)

open Lwt.Infix

let port = if Array.length Sys.argv > 1 then int_of_string (Sys.argv.(1)) else 16384
let s = Lwt_io.establish_server_with_client_address (Unix.ADDR_INET(Unix.inet_addr_any, port)) ChatServer.chat_server
let _ = Lwt_main.run (fst (Lwt.wait ()))
let _ = s >>= Lwt_io.shutdown_server (* never executes; you might want to use it in utop, though *)

The result should be that when running the program, it will:

• print a welcome message to outp,
• read the nick from inp,
• assign the new value to nr
• Add nr to sessions
• Announce that the user has joined.

Right now, it compiles, but does not output anything.