MQtt REST Translator, a MQTT<->REST bridge dameon. The main aim of this daemon to act as a glue layer between your IOT devices (communicating via MQTT), and your web application, on a general way, meaning that the mqrestt deamon logic doesn't have to know too much neither about your MQTT topics and neither about your webapplication's URIs. To price to pay for this is that you have some correlation between your MQTT topics and your URIs, which is probably the sensible thing to do in any system using both MQTT and REST. The working principle is to forward MQTT messages as HTTP POST request to a web application, and vice versa, acting as a simple HTTP server, which receives POST requests, and publish the messages via MQTT. In the MQTT->REST case the URI of the POST call is fabricated from the MQTT topic the message was received on, and the body is the MQTT message itself. In the REST->MQTT case similarly, the MQTT topic is fabricated based on the URI of the incoming request. The 2 use-case can run simultaneously, and each can have multiple units configured, therefore it's possible to subscribe to 2 different topics and forward the messages to different web applications living on different hosts. Therefore it's also possible to have different projects/products connecting to the same MQTT broker, and running one instance of mqrestt, but 2 web applications managing the different networks.
mqrestt is implemented in C (C99 standard), in order to be able to run
low-level platforms such as SOHO routers running OpenWrt. mqrestt depends
heavily on a number of libraries to implement its funcionality, namely
libmosquitto, libconfuse, libmicrohttpd and libcurl. All of these
dependencies are well-known open source libraries, available for most of
the OS-s and hardware platforms. The main target OS is Linux, but it
should be easy to get it run on any OS, as long as the mentioned
dependencies are available.
The simplest configuration is to subscribe to one MQTT topic, and forward the received messages to the API server, as shown here:
MQTT pub
'/devices/12/temperature' MQTT sub HTTP POST
.--------------. '/' 'https://myapp.com/api/devices/12/temperature'
| Sensor Nodes | .-------------. .---------. .------------------.
'--------------'---------->| MQTT broker |---->| MQresTT |----------->| Web API server |
'--------------' '-------------' '---------' '------------------'
'--------------'
In this case, MQresTT is configured to subscribe to all of the MQTT messages in all topics (as '/'), and the messages are forwarded to the base URI 'https://myapp.com/api', which base URI is extended with the MQTT topic of the message. The payload of the HTTP POST is the content of the MQTT message as is. See the sample mqrestt.conf to implement this without any auth or SSL enabled at doc/simple_mqtt2rest__mqrestt.conf
0.1: - MQTT->REST support - REST->MQTT support
0.2 - SSL support both MQTT and HTTPs - rewrite support, to rewrite MQTT topics into URL's and vica verse (a'la Apache mod_rewrite)
https://iot.stackexchange.com/questions/3763/restapi-and-mqtt-broker
https://mosquitto.org/api/files/mosquitto-h.html
Development dependencies (on Debian/Ubuntu): autoconf-archive libcurl4-openssl-dev libmosquitto-dev libconfuse-dev libconfuse-dev