example-spa-elm-app/frontend/src/Ports.elm

port module Ports exposing
    ( socketOnEvent
    , socketSend
    , socketOpen
    )

import Websockets
import Json.Encode as Encode

port webSocketCommand : Websockets.CommandPort msg
port webSocketEvent : Websockets.EventPort msg

socketName : String
socketName = "app"

socketOnEvent : Websockets.EventHandlers msg -> Sub msg
socketOnEvent eventHandlers =
    socket.onEvent eventHandlers

socketSend : Encode.Value -> Cmd msg
socketSend data  = socket.send socketName data

socketOpen : Cmd msg
socketOpen = socket.open socketName "/ws/" []

socket : Websockets.Methods msg
socket =
    Websockets.withPorts
        { command = webSocketCommand
        , event = webSocketEvent
        }