WebSocket Server

Web Socket Server in Elm and Node.js

Installation

To install the elm part of this library run:

elm package install RGBboy/websocket-server

To install the node part of this library run:

npm install elm-websocket-server

Usage

See the example folder for a working version.

To get this working run:

npm install
npm run build:example
npm run start:example

Then go to localhost:8080 in multiple browser windows.

Example Elm Server Program

port module Server exposing (..)

import Platform exposing (Program)
import Json.Decode as Decode
import Json.Encode as Encode
import WebSocketServer as WSS exposing (Socket, sendToOne, sendToMany)



main : Program () Model Msg
main =
  Platform.worker
    { init = always ([], Cmd.none)
    , update = update
    , subscriptions = subscriptions
    }

-- PORTS

port inputPort : (Decode.Value -> msg) -> Sub msg
port outputPort : Encode.Value -> Cmd msg

-- MODEL

type alias Model = List WSS.Socket

-- UPDATE

type Msg
  = Connection WSS.Socket
  | Disconnection WSS.Socket
  | Message String
  | Noop

update : Msg -> Model -> (Model, Cmd msg)
update message model =
  case (Debug.log "Msg" message) of
    Connection socket ->
      ( socket :: model
      , Cmd.none
      )
    Disconnection socket ->
      ( List.filter ((/=) socket) model
      , Cmd.none
      )
    Message clientMessage ->
      ( model
      , WSS.sendToMany outputPort clientMessage model
          |> Cmd.batch
      )
    Noop -> (model, Cmd.none)

-- SUBSCRIPTIONS

decodeMsg : Decode.Value -> Msg
decodeMsg value =
  let
    decoder = WSS.eventDecoder
      { onConnection = (\socket _ -> Connection socket)
      , onDisconnection = (\socket _ -> Disconnection socket)
      , onMessage = (\_ _ message -> Message message)
      }
  in
    Decode.decodeValue decoder value
      |> Result.withDefault Noop

subscriptions : Model -> Sub Msg
subscriptions model = inputPort decodeMsg

Example Usage in Node.js

The node API for this is quite simple:

var port = (process.env.PORT || 8080),
    server = require('http').createServer(),
    WebSocketServer = require('elm-websocket-server'),
    app = require('./my-elm-server.js').Elm.Server.init(),
    wss = new WebSocketServer(
      server,
      app.ports.inputPort,
      app.ports.outputPort
    );

server.listen(port);

console.log(`Listening on :${port}`);

Development

Run npm install then elm package install.

Tests

Run npm test.