mqtt_ehealth_client

Integrating the e-health sensors functions in the Paho C++ client for MQTT in order to send data to a remote broker on a Raspberry Pi. This fixes most issues that I found trying to deal with the C++ Paho library. All this project does is retrieve data from the sensors and send it to a broker, using the airflow.cpp example (with fake data in order to work on any device).

As a school project, I'm also temporarily going to list everything that I had to do in order to set up my VPS, which now hosts the broker, the MongoDB database, the restAPI as well as the website. It may then move to a Gist later on.

See https://github.com/ojathelonius/mqtt_ehealth_subscriber to have an overview of how to subscribe to the broker using NodeJS.

Important note : the master branch allows simulating data received from eHealth sensors. The dev branch allows you to receive actual data from the sensors, thus includes eHealth and arduPi libraries. Please check out the dev branch if you want to make it work on a Raspberry.

Getting started

Install openSSL

sudo apt-get install libssl-dev

Install Paho C client

git clone https://github.com/eclipse/paho.mqtt.c.git
sudo make install

Install Paho C++ client

git clone https://github.com/eclipse/paho.mqtt.cpp.git
sudo make

Manually adding lib files in /usr/local/lib/

• Copying files

cd paho.mqtt.cpp/lib
sudo cp -r . /usr/local/lib

• Updating ld

sudo ldconfig

Cloning the client on the Raspberry

git clone https://github.com/ojathelonius/mqtt_ehealth_client.git

Modify the mqtt_client_config.JSON file to add your broker IP, credentials and options

Compile a sensor C++ file (e.g. airflow.cpp)

sudo make

Note : if you add sensor files, make sure you also add them in the Makefile (add & clean)

Start retrieving sensor data and sending it to the broker

./example

See https://www.cloudmqtt.com/ for a free hosted broker. Or see below to learn how to host your own mosquitto broker (on a VPS for instance).

Host your own Mosquitto broker

• Install Mosquitto (on your VPS)

apt-get update
apt-get install build-essential libwrap0-dev libssl-dev libc-ares-dev uuid-dev xsltproc
sudo apt-get install mosquitto

• Create a new user and store its credentials in a password file

mosquitto_passwd -c /etc/mosquitto/pwfile

• Create a new configuration file from the example

cp /etc/mosquitto/mosquitto.conf.example /etc/mosquitto/mosquitto.conf
nano /etc/mosquitto/mosquitto.conf

• Add your own info in mosquitto.conf

listener 1883 <VPS_IP>
connection_messages true
log_timestamp true
allow_anonymous false
password_file /etc/mosquitto/pwfile

• Update links

/sbin/ldconfig

• Start the broker in the background

mosquitto -c /etc/mosquitto/mosquitto.conf -d 

Test it

• If you didn't install your own broker

sudo apt-get install mosquitto-dev
sudo apt-get install mosquitto-clients
sudo service mosquitto start
mosquitto_sub -h 127.0.0.1 -t <topic>

• With your own broker

mosquitto_sub -h <broker_adress> -P <port> -t <topic> -u <user> -p <password> 

Allow WebSocket in Mosquitto to display real-time data in a browser

The Paho Javascript library allows you to retrieve real-time data from the broker using WebSockets. However mosquitto 1.4.10, which is available through apt-get, doesn't allow websockets. We need to build mosquitto 1.4.x (using Mosquitto 1.4.2 here) manually.

• Install libwebsockets We prepare the build system.

sudo apt-get update
sudo apt-get install build-essential python quilt devscripts python-setuptools python3
sudo apt-get install libssl-dev
sudo apt-get install cmake
sudo apt-get install libc-ares-dev
sudo apt-get install uuid-dev
sudo apt-get install daemon

Then we download, build and install libwebsockets.

wget http://git.libwebsockets.org/cgi-bin/cgit/libwebsockets/snapshot/libwebsockets-1.4-chrome43-firefox-36.tar.gz
tar zxvf libwebsockets-1.4-chrome43-firefox-36.tar.gz
cd libwebsockets-1.4-chrome43-firefox-36
mkdir build
cd build
cmake ..
sudo make install
sudo ldconfig

• Installing Mosquitto 1.4.2

wget http://mosquitto.org/files/source/mosquitto-1.4.2.tar.gz
tar zxvf mosquitto-1.4.2.tar.gz
cd mosquitto-1.4.2

Modify config.mk by replacing WITH_WEBSOCKETS:=no with WITH_WEBSOCKETS:=yes , then :

make
sudo make install

• Adding the WebSocket port in mosquitto.conf

nano /etc/mosquitto/mosquitto.conf

Modify mosquitto.conf by adding the two following lines :

port 1884
protocol websockets

Make sure you keep the default port (1883) if you want to keep subscribing with your other MQTT clients.

• Restart the mosquitto service

sudo service mosquitto stop
mosquitto -c /etc/mosquitto/mosquitto.conf -d 

Et voilà !

Host several NodeJS apps with various subdomain names on the same VPS

• Create DNS entries for each subdomains (e.g. app.domain.com, api.domain.com ) in your hosting service manager
• Install nginx on your VPS

sudo apt-get install nginx

• Create as many configuration files as NodeJS apps you want to run

nano /etc/nginx/conf.d/app1.conf
nano /etc/nginx/conf.d/app2.conf

• And use the following template for each :

server {
    listen 80;
 
    server_name subdomain_you_want_to_use;
 
    location / {
        proxy_pass http://localhost:<port_of_the_app>;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        proxy_set_header Host $host;
        proxy_cache_bypass $http_upgrade;
    }
}

• Restart nginx service

sudo service nginx restart

• Start all those apps with forever. All done !