stop using a hardcoded websocket address in ws_client

src/ws_client.ml

@@ -5,8 +5,14 @@ open Shared
 let ws =
   Format.printf "create websocket@\n";
   let ws_url =
-    (* TODO fix hostname *)
+    let location = Window.location G.window in
-    Jstr.of_string "ws://localhost:3696/island/ws"
+    let host = Uri.host location |> Jstr.to_string in
+    let port =
+      Option.fold ~none:""
+        ~some:(fun port -> Format.sprintf ":%d" port)
+        (Uri.port location)
+    in
+    Jstr.of_string @@ Format.sprintf "ws://%s%s/island/ws" host port
   in
   Websocket.create ws_url