bisquitt

Bisquitt is a transparent MQTT-SN gateway. It provides a simple, secure, and standards-based way to connect resource-constrained IoT devices to MQTT infrastructure.

Bisquitt supports most MQTT-SN 1.2 features, allows secure communication using DTLS 1.2, and implements an authentication extension based on MQTT-SN 2.0 draft.

Besides the gateway, Bisquitt provides bisquitt-sub and bisquitt-pub command-line MQTT-SN clients and can be used as a Go MQTT-SN library.

Installation

The easiest way to install Bisquitt is to use its Docker image:

$ docker pull energomonitor/bisquitt

The image contains the gateway itself (bisquitt), which is started by default, and the command-line MQTT-SN clients (bisquitt-sub and bisquitt-pub).

Alternatively, you can install the gateway and clients using go install:

$ go install github.com/energomonitor/bisquitt/cmd/bisquitt@latest
$ go install github.com/energomonitor/bisquitt/cmd/bisquitt-pub@latest
$ go install github.com/energomonitor/bisquitt/cmd/bisquitt-sub@latest

Note that Bisquitt requires Go 1.16 or higher.

Let us know if you'd like to have additional installation formats available.

Usage

The best way to start with Bisquitt is to run it together with Mosquitto (an open-source MQTT server) using Docker Compose:

1. Create a mosquitto.conf file with the following contents:

   listener 1883 0.0.0.0
   allow_anonymous true
   

2. Create a docker-compose.yml file with the following contents:

   version: "3.7"
   
   services:
     bisquitt:
       image: energomonitor/bisquitt
       environment:
         MQTT_HOST: mosquitto
         BISQUITT_USER: bisquitt
         BISQUITT_GROUP: bisquitt
       ports:
         - "1883:1883/udp"
       depends_on:
         - mosquitto
   
     mosquitto:
       image: eclipse-mosquitto
       ports:
         - "1883:1883"
       volumes:
         - ./mosquitto.conf:/mosquitto/config/mosquitto.conf
   

3. Run the services:

   $ docker-compose up
   

You can now play with Bisquitt using bisquitt-sub and bisquitt-pub command-line MQTT-SN clients. Open a new terminal and open a shell in the bisquitt service container:

$ docker-compose exec bisquitt sh

Inside this shell, use bisquitt-sub to subscribe to a topic:

# bisquitt-sub -t my-topic

Now open another shell in the bisquitt service container:

$ docker-compose exec bisquitt sh

Inside the second shell, use bisquitt-pub to send a message to the topic you've subscribed to:

# bisquitt-pub -t my-topic -m message

You should see the following output in the first shell:

my-topic: message

Voilà! You've just sent a message to an MQTT server via an MQTT-SN gateway from one client and received it back in another one.

If you are interested in what's going on under the hood, add the --debug option to any of the commands above.

For more information on usage, use the --help option on bisquitt, bisquitt-sub or bisquitt-pub:

# bisquitt --help
# bisquitt-pub --help
# bisquitt-sub --help

Once you are done playing with Bisquitt, shut down the services:

$ docker-compose down

Features

Bisquitt is a transparent MQTT-SN gateway. This means that the gateway maintains one connection to an MQTT server for every connected MQTT-SN client. An MQTT-SN client can therefore be treated like any other MQTT client on the MQTT server side (for purposes such as authentication, topics access management, or monitoring).

The implementation is based on MQTT-SN 1.2. Its specification is a bit unclear in some places, which required interpretation.

Supported MQTT-SN features

• Connecting and disconnecting (CONNECT, CONNACK, DISCONNECT)
• Topic registration (REGISTER, REGACK)
• Publishing (PUBLISH, PUBACK, PUBCOMP, PUBREC, PUBREL)
• Subscribing (SUBSCRIBE, SUBACK)
• Last will (WILLTOPICREQ, WILLTOPIC, WILLMSGREQ, WILLMSG)
• Keep alive (PINGREQ, PINGRESP)
• QoS levels -1, 0, 1, 2
• Sleeping clients

Supported MQTT-SN extensions

• Authentication (AUTH, based on the MQTT-SN 2.0 draft and described separately)
• DTLS 1.2

Planned MQTT-SN features

• Support for MQTT-SN 2.0

Unsupported MQTT-SN features

• Last will change (WILLTOPICUPD, WILLTOPICRESP, WILLMSGUPD, WILLMSGRESP)
• Gateway advertisement and discovery (ADVERTISE, SEARCHGW, GWINFO)
• Message forwarding

Limitations

• Bisquitt currently does not persist state between service restarts. This means it can't guarantee to preserve conversation state, last will messages, and topics in all situations. We plan to implement this soon.

• DTLS certificates can't be reloaded without a service restart.

Thanks

Bisquitt is inspired and partially based on gnatt. Thank you!

License

Bisquitt is distributed under Eclipse Public License 2.0. See LICENSE for more information.

Code in the util/crypto directory is distributed under the MIT license. See LICENSE there for more information.