REVIEW: Telemetry Transport Sample Application

TL;DR MQTT Sample IoT Application is a Nitro N2O pages that works on top of MQTT connection between browser and server.

Intro

Sample application consist of two pages login and index. It creates WebSocket MQTT connection to emqttd server which is dependency of n2o. The permanent example is accesible at review.n2o.dev/index.htm.

Index

Init event.

event(init) ->
    nitro:wire("nodes="++nitro:to_list(length(n2o:ring()))++";"),
    #cx{session=Token,params=Id,node=Node} = get(context),
    Room = n2o:session(room),
    nitro:update(logout,
      #button { id=logout, body="Logout " ++ n2o:user(),postback=logout}),
    nitro:update(send,
      #button { id=send, body="Chat", source=[message], postback=chat}),
    nitro:update(heading, #h2 { id=heading, body=Room}),
    nitro:update(upload, #upload { id=upload   }),
    nitro:wire("mqtt.subscribe('room/"++Room++"',subscribeOptions);"),
    Topic = iolist_to_binary(["events/1/",Node,"/index/anon/",Id,"/",Token]),
    n2o:send_reply(<<>>, 2, Topic, term_to_binary(#client{id=Room,data=list})),
    nitro:wire(#jq{target=message,method=[focus,select]});

Chat event.

event(chat) ->
    User    = n2o:user(),
    Message = n2o:q(message),
    Room    = n2o:session(room),
    #cx{session=ClientId} = get(context),
    io:format("Chat pressed: ~p\r~n",[{Room,ClientId,Message,User}]),
    kvs:add(#entry{id=kvs:next_id("entry",1),
                   from=n2o:user(),feed_id={room,Room},media=Message}),

    nitro:insert_top(history, nitro:jse(message_view(User,Message))),
    Actions = iolist_to_binary(n2o_nitro:render_actions(n2o:actions())),
    M = term_to_binary({io,Actions,<<>>}),
    n2o:send_reply(ClientId, 2, iolist_to_binary([<<"room/">>,Room]), M);

Client event.

event(#client{id=Room,data=list}) ->
    [ nitro:insert_top(history, nitro:jse(message_view(E#entry.from,E#entry.media)))
      || E <- lists:reverse(kvs:entries(kvs:get(feed,{room,Room}),entry,30)) ];

FTP event.

event(#ftp{sid=_Sid,filename=Filename,status={event,stop}}=Data) ->
    io:format("FTP Delivered ~p~n",[Data]),
    Name = hd(lists:reverse(string:tokens(nitro:to_list(Filename),"/"))),
    IP = application:get_env(review,host,"127.0.0.1"),
    erlang:put(message,
    nitro:render(#link{href=iolist_to_binary(["http://",IP,":8000/ftp/",
                       nitro_conv:url_encode(Name)]),body=Name})),
    event(chat);

Login

Channel init.

event(init) ->
    nitro:wire("nodes="++nitro:to_list(length(n2o:ring()))++";"),
    nitro:update(loginButton,
          #button { id=loginButton, body="login",
                    postback=login,source=[user,pass]});

Login event.

event(login) ->
    User = nitro:to_list(n2o:q(user)),
    Room = nitro:to_list(n2o:q(pass)),
    n2o:user(User),
    n2o:session(room,Room),
    nitro:redirect("/index.htm");

Setup

To run review application just clone, build and run:

$ git clone git://github.com/synrc/review && cd review
$ mix deps.get
$ iex -S mix

Then open it in browser:

$ open http://127.0.0.1:8000/app/index.html

Credits

• Brought with ❤ by N2O community