# How to use WebSocket.webSocket class in ocsigen? **URL:** \ **Category:** Learning\ **Tags:** ocsigen\ **Created:** [January 3, 2018, 11:40am UTC](https://discuss.ocaml.org/t/how-to-use-websocket-websocket-class-in-ocsigen/1385 "2018-01-03T11:40:27Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![tidou](https://avatars.discourse-cdn.com/v4/letter/t/90db22/32.png) [@tidou](https://discuss.ocaml.org/u/tidou)\ **Post date:** [January 3, 2018, 11:40am UTC](https://discuss.ocaml.org/t/how-to-use-websocket-websocket-class-in-ocsigen/1385/1 "2018-01-03T11:40:27Z")
Hello everyone! I tried to read a json file from disk and send it as a string to the client in ocsigen. Because after getting longer than 100 lines in my opinion every code file becomes a hell of mess to understand I decided to separate the client code from `main.eliom` file and put it into `client.ml` and in main.eliom I created a function like: ```auto let read_json path = let json = Yojson.Basic.from_file path in Yojson.Basic.Util.to_string json ``` and when I wanted to call it in `client.ml` like: `~%read_json "./static/js/data.json"` I got the error: ```auto Error: Unbound value ~% Makefile:208: recipe for target '_client/client.cmo' failed ``` Then I changed my mind to use websocket for rpc and I found WebSocket.webSocket class in js\_of\_ocaml without any example of how to use it I tried in client and server code this line of code: ```auto let ws_obj = (new WebSockets.webSocket)#url "ws://localhost:8080/json" ``` in fact without being able to get any results but the error: ```auto Error: Unbound class WebSockets.webSocket ``` how to make a simple websocket server and use it on client side in two separate files? any help would be very appreciated. Thanks in advance. ---
**Author:** ![jpdeplaix](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/jpdeplaix/32/780_2.png) [@jpdeplaix](https://discuss.ocaml.org/u/jpdeplaix)\ **Post date:** [January 4, 2018, 12:08pm UTC](https://discuss.ocaml.org/t/how-to-use-websocket-websocket-class-in-ocsigen/1385/2 "2018-01-04T12:08:12Z")
I won’t be of very much help on the compilation errors but the websocket module is more or less a straight translation from the WebSocket API: [https://developer.mozilla.org/en-US/docs/Web/API/WebSocket](https://developer.mozilla.org/en-US/docs/Web/API/WebSocket) As the original author of this module I’m really sorry about the lack of documentation. ---
**Author:** ![tidou](https://avatars.discourse-cdn.com/v4/letter/t/90db22/32.png) [@tidou](https://discuss.ocaml.org/u/tidou)\ **Post date:** [January 4, 2018, 12:15pm UTC](https://discuss.ocaml.org/t/how-to-use-websocket-websocket-class-in-ocsigen/1385/3 "2018-01-04T12:15:43Z")
For calling a server-side function from a client-side code in a separate file you can do this for this example in `main.eliom` file add: ```auto let read_json path = let json = Yojson.Basic.from_file path in Lwt.return (Yojson.Basic.to_string json) let%client read_json = ~%(Eliom_client.server_function [%derive.json : string] read_json) ``` then you can call **read\_json** in `client.ml` file as: ```auto open Main ... let%lwt jsn = read_json "file.json" ... ``` but please help me with WebSockets.webSocket, Thanks! ---
**Author:** ![jpdeplaix](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/jpdeplaix/32/780_2.png) [@jpdeplaix](https://discuss.ocaml.org/u/jpdeplaix)\ **Post date:** [January 4, 2018, 12:18pm UTC](https://discuss.ocaml.org/t/how-to-use-websocket-websocket-class-in-ocsigen/1385/4 "2018-01-04T12:18:57Z")
Mmh I just noticed that you were talking about server-side websockets as well. The `WebSockets` module is client side only (everything in js\_of\_ocaml is). Rereading was a bit helpful in fact. The `Error: Unbound class WebSockets.webSocket` comes from the fact that `WebSockets.webSocket` is not a class but a JS constructor and cannot be instantiate but the `new%js constr e1 ... en` construct should be used instead. See [http://ocsigen.org/js\_of\_ocaml/2.8.4/api/Ppx\_js](http://ocsigen.org/js_of_ocaml/2.8.4/api/Ppx_js) for more “technical” documentation about the syntax extension. ---
**Author:** ![tidou](https://avatars.discourse-cdn.com/v4/letter/t/90db22/32.png) [@tidou](https://discuss.ocaml.org/u/tidou)\ **Post date:** [January 4, 2018, 12:23pm UTC](https://discuss.ocaml.org/t/how-to-use-websocket-websocket-class-in-ocsigen/1385/5 "2018-01-04T12:23:02Z")
Thank you! I will try to write a websocket server with other capabilities of OCaml. Thanks for your help of how to use `WebSocket.webSocket` by `new%js` and Happy New Year! ---
**Author:** ![jpdeplaix](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/jpdeplaix/32/780_2.png) [@jpdeplaix](https://discuss.ocaml.org/u/jpdeplaix)\ **Post date:** [January 4, 2018, 12:25pm UTC](https://discuss.ocaml.org/t/how-to-use-websocket-websocket-class-in-ocsigen/1385/6 "2018-01-04T12:25:33Z")
I believe this library is already doing websockets on server-side: [https://github.com/vbmithr/ocaml-websocket](https://github.com/vbmithr/ocaml-websocket) It is available via opam by doing: `opam install websocket` or `opam install websocket-lwt` Happy new year to you too. ---
**Author:** ![olleharstedt](https://avatars.discourse-cdn.com/v4/letter/o/f1d935/32.png) [@olleharstedt](https://discuss.ocaml.org/u/olleharstedt)\ **Post date:** [May 24, 2020, 10:43pm UTC](https://discuss.ocaml.org/t/how-to-use-websocket-websocket-class-in-ocsigen/1385/7 "2020-05-24T22:43:10Z")
Did anyone manager to use the ocaml-websocket library? I tried and got header problems, possibly because of no SSL setup on my localhost. ---
**Author:** ![Levi\_Roth](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/levi_roth/32/2268_2.png) [@Levi\_Roth](https://discuss.ocaml.org/u/Levi_Roth)\ **Post date:** [May 24, 2020, 11:57pm UTC](https://discuss.ocaml.org/t/how-to-use-websocket-websocket-class-in-ocsigen/1385/8 "2020-05-24T23:57:54Z")
I used it successfully a couple years ago. The code is probably a mess, but you can see the server side of things [here](https://github.com/leviroth/backgammon/blob/52386adad48e98105058be1f9753f9acfc8673ef/server/main.ml), and (though it doesn’t use the OCaml library) it’s accessed on the browser side [here](https://github.com/leviroth/backgammon/blob/master/client/main.ml).