Re: [m2m-iwg] MQTT <-> REST+websocket mapping

[Peter Niblett <peter_niblett@xxxxxxxxxx>]

Hi Matteo

I think there's been some parallel discussion
of your first point on the Paho mailing list. I am curious about your remarks
about tunnelling MQTT over websockets.  Since RFC6455 is a binary
protocol, it seems a more natural fit to run binary MQTT over it. That
way
a) We avoid having to specify and standardise
a new version of MQTT
b) Applications that are operating under
tight bandwidth constraints can still do so, without suffering the increase
in message size that JSON would imply

I'm only talking about the headers here.
If you want to use JSON to encode the application data (i.e. send JSON
in an MQTT message) that's fine, and of course you might well want to do
that even when running MQTT directly over TCP/IP.

Regards 


Peter Niblett
IBM Senior Technical Staff Member
Member of the IBM Academy of Technology
+44 1962 815055
+44 7825 657662 (mobile)




From:      
 Matteo Collina <matteo.collina@xxxxxxxxx>
To:      
 m2m Industry Working
Group <m2m-iwg@xxxxxxxxxxx>, 
Date:      
 03/15/2013 02:53 PM
Subject:    
   [m2m-iwg] MQTT
<-> REST+websocket mapping
Sent by:    
   m2m-iwg-bounces@xxxxxxxxxxx

---

Hi Everyone,

I am working on a web adapter for MQTT, and in general
to the whole Internet of Things and M2M worlds. My preliminary work is
available at: http://qest.me/.
It seems everyone is working on this problem, however
there is not a shared effort on it, and it is time to reignite the discussion.

I am identifying the requirements for a general solution
to this problem:
1) Web-tunnelling of MQTT to achieve compatibility with
web apps..
2) REST interface that must enable to read and write the
last message from a topic.
3) REST interface to read the history of the messages
on a topic/query.
4) No modification to MQTT and pluggable to any MQTT server.
5) Security & Access Control Systems.
6) Support for webhooks, to ease the integration in other
server-side systems.

In order to clarify more, I will expand some points.

1) The websocket tunneling issue is longstanding in this
community. Some previous attempt has been done, and there was even a proposal
for routing binary MQTT inside a websocket tunnel.
I believe that the best approach to make this work is
to map MQTT to JSON in a standard way, and then route it inside websocket
& polyfills (es. socket.io
or sock.js and the like)
This will simplify implementations and diffusion. 

2) While creating an interface for publishing messages
is easy, the core issue is on reading them.
For example, ActiveMQ uses a DELETE to read a message,
which can timeout if no message is published in a given period of time.
This approach is not really web-compatible, so QEST adopt a standard GET
approach, exposing to the web every published message (here you can find
is my home temperature: http://qest.me/topics/temp).
Every message is stored on a Redis database.
However, exposing the last message on the web is extremely
similar to the retained message behavior. In QEST, I did assimilate
the two concepts stating that every message is retained, even on MQTT.
At the moment, I am revising this decision to be MQTT-compliant.
Still, the web behavior needs to be clear. One possible solution is to
expose on the web only retained messages, or ignore the 'retained' flag
at the web level and expose everything.

3) An History interface has to be provided. The best work
done in that area is Cosm.
However, a standard representation of message meta-data
has to be defined.

5) There is much discussion on how to expose M2M and IoT
to end users. Exposing it to the web is a key point, and doing it a safe
way for both users and devices is extremely important.
In particular, both the provisioning of devices and the
pairing between users and devices must be addressed.
This will necessarily lead to a paring protocol on top
of both MQTT and HTTP, and might include an OAuth step.

Have you got some suggestions on these topics?

Cheers,

Matteo_______________________________________________
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