Oblast IoT platform

Oblast is a lightweight IoT platform following the publish/subscribe design pattern. The architecture consists of

• a central server - responsible of collecting and distributing the updates and
• a list of clients. Each client can publish or subscribe (or both) to a named variable.

Two client API are provided:

• a Python3 module to write your own custom publisher and subscriber (e.g on a Raspberry PI)
• a C++ library to write (embedded) clients (e.g. on an Arduino development board)

Automatic network discovery:

Once the server is started, it listens to UDP port 1292 and TCP port 1291 (don't forget to create a firewall rule for them). The UDP socket is used for the client to discover the server's IP address using a multicast query. Once the server is located, the clients are instructed to connect using a TCP channel.

Global variable names:

Each publisher first subscribe to a given variable name. These names are unique for the whole platform. The value can then be manipulated at the programmer's convenience and updates are automatically sent to the server who propagates them to the other subscribers.

subscribe to variables

A standard client would register to a set of specific variables using a subscribe call. Each variable is indentified by a system-wide name.

Oblast API provides also the ability for a client to subscribe to all existing (and future) variables. This is typically useful for having an overview of the state of the system and possibly to store data in a database.

How to start the server:

To compile the server, go to the server/ folder and use make:

cd server;
make;

Open the necessary ports using ufw:

sudo ufw allow 1291:1292/udp

Finally run the server:

./bin/oblast

How to write a client:

To see the full example, open clientAPI/python/producer.py. Here is a step by step walk-through:

First the client needs to create a connection using an OblastConnection object. Then it needs to use that connection to subscribe to a given variable with a suitable name (in the following examle, called "foo_var"). Finally it periodically updates the variable value - maybe reading from a sensor - using the set function. The client should also yield its execution and let the connection handle the variable updates (handle_updates() below).

# simplified extract from clientAPI/python/producer.py:
with OblastConnection() as connection:
    foo_var = connection.subscribe("foo_var", reactor)
    while True:
        connection.handle_updates()
        foo_var.set("42")
        time.sleep(1)

NodeMCU / ESP8266 demo:

An analogous implementation for Arduino (or NodeMCU) can be found in the clientAPI/nodeMCU/ folder. In particular, clientAPI/nodeMCU/dht22/dht22.ino illustrates how to use an ESP8266 to measure temperature / humidity data and to publish them to Oblast infrastructure.

Setting a service on Raspberrypi

Write the following file (as root) into /etc/systemd/system/oblast.service:

[Unit]
Description=Oblast service

[Service]
User=pi
WorkingDirectory=/home/pi/Documents/Oblast/server
ExecStart=/home/pi/Documents/Oblast/server/bin/oblast
Restart=Always
RestartSec=3

[Install]
WantedBy=multi-user.target                         

Restart the daemon (systemctl daemon-reload) and then start the service systemctl start oblast.service

Logs of Oblast:

To see the logs, use

sudo journalctl -u oblast