https://github.com/evancz/elm-http/issues/34

34-DifferentPort.elm

module Main exposing (..)

import Html
import Html.App
import Html.Events
import Http
import Json.Decode as Json exposing ((:=))
import Task


url : String
url =
    "http://localhost:8000/"


type alias Model =
    { content : String
    }


init : ( Model, Cmd Msg )
init =
    ( Model "", Cmd.none )


type Msg
    = Retrieve
    | RetrieveSuccess String
    | RetrieveFail Http.Error


update : Msg -> Model -> ( Model, Cmd Msg )
update message model =
    case message of
        Retrieve ->
            ( model, getData url )

        RetrieveSuccess content ->
            ( { model | content = content }, Cmd.none )

        RetrieveFail error ->
            ( { model | content = "error" }, Cmd.none )


getData : String -> Cmd Msg
getData url =
    Task.perform RetrieveFail RetrieveSuccess (Http.getString url)


view : Model -> Html.Html Msg
view model =
    Html.div
        []
        [ Html.text ("result: " ++ model.content)
        , Html.br [] []
        , Html.button [ Html.Events.onClick Retrieve ] [ Html.text "Request data" ]
        ]


main =
    Html.App.program
        { init = init
        , view = view
        , update = update
        , subscriptions = \_ -> Sub.none
        }