test.ml

let handle_ws_message msg =
    Lwt_io.printf "> %s\n" msg

let connect uri =
    let%lwt endp = Resolver_lwt.resolve_uri ~uri Resolver_lwt_unix.system in
    let ctx = Lazy.force Conduit_lwt_unix.default_ctx in
    let%lwt client = Conduit_lwt_unix.endp_to_client ~ctx endp in
    let%lwt conn = Websocket_lwt_unix.connect ~ctx client uri in
    let rec handle_ws_input msg_content =
        let%lwt frame = Websocket_lwt_unix.read conn in
        let open Websocket in
        match frame with
        | {Frame.opcode = Ping; _} ->
                let%lwt () = Websocket_lwt_unix.write conn
                                (Websocket.Frame.create ~opcode:Pong ()) in
                handle_ws_input msg_content
        | {Frame.opcode = Pong; _} ->
                handle_ws_input msg_content
        | {Frame.opcode = Text; Frame.final = true; content; _}
        | {Frame.opcode = Binary; Frame.final = true; content; _} ->
                handle_ws_message (msg_content ^ content);
                handle_ws_input ""
        | {Frame.opcode = Text; Frame.final = false; content; _}
        | {Frame.opcode = Binary; Frame.final = false; content; _} ->
                handle_ws_input (msg_content ^ content)
        | _ -> Websocket_lwt_unix.close_transport conn in
    handle_ws_input ""

(*
 * File "test.ml", line 23, characters 16-57:
 * 23 |                 handle_ws_message (msg_content ^ content);
 *                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 * Warning 10 [non-unit-statement]: this expression should have type unit.
 *)