Server.Websocket
type elt = [ `Connection_close | `Msg of [ `Continuation | `Text | `Binary ] * bool | `Other | `Ping | `Pong ] * string
type ic = unit -> elt option
type oc = elt -> unit
type stop
val stop : unit -> stop
val switch : stop -> unit
val upgrade : ?stop:stop -> fn:(ic -> oc -> unit) -> flow -> unit