Log in with your non-root user and use the yum package manager to install the epel-release package.
$ sudo yum -y install epel-release
This adds the EPEL repository information to our system. The -y option automatically answers yes to a few prompts throughout the process. Now we can install the mosquitto package.
$ sudo yum -y install epel-release
Edit the /etc/mosquitto/mosquitto.conf
We will have persistent storage for client subscribing to the queues. It sounds good to activate client expiration to ensure we won’t have unlimited persistence.
persistent_client_expiration 15d
The messages are firstly stored in memory then saved on disk after the autosave interval second. The default value is 30 minutes (1800s) and it create a risk of large loss. A reduction to 1-minute sound safer.
autosave_interval 60persistence truepersistence_file mosquitto.dbpersistence_location /var/lib/mosquitto/
Create the directory for persistence DB if not yet existing
mkdir /var/lib/mosquitto/chown mosquitto:mosquitto /var/lib/mosquitto/
$ service mosquitto start
$ systemctl enable mosquitto
Topics are labels that you publish messages to and subscribe to. They are arranged as a hierarchy, so you could have sensors/outside/temp and sensors/outside/humidity, for example. How you arrange topics is up to you and your needs. Throughout this tutorial we will use a simple test topic to test our configuration changes.
Log in to your server a second time, so you have two terminals side-by-side. In the new terminal, use mosquitto_sub to subscribe to the test topic:
$ mosquitto_sub -h localhost -t test
-h is used to specify the hostname of the MQTT server, and -t is the topic name. You’ll see no output after hitting ENTER because mosquitto_sub is waiting for messages to arrive. Switch back to your other terminal and publish a message:
$ mosquitto_pub -h localhost -t test -m “hello world”
The options for mosquitto_pub are the same as mosquitto_sub, though this time we use the additional -m option to specify our message. Hit ENTER, and you should see hello world pop up in the other terminal. You’ve sent your first MQTT message!
Enter CTRL+C in the second terminal to exit out of mosquitto_sub, but keep the connection to the server open.
Requirements:
once you have centos installed you will need to make sure it has been updated.
$ sudo yum update -y
install Node.JS and npm
$ sudo yum install nodejs
install Node-Red
$ sudo npm install -g node-red
Now let’s set it up as a service so that it will automatically start
sudo vi /etc/systemd/system/node-red.service
[Unit]Description=Node-REDAfter=network.target [Service]Type=simpleExecStart=/usr/local/bin/node-red-pi –max-old-space-size=128 -vRestart=on-failureKillSignal=SIGINT WorkingDirectory=/home/amolUser=amol [Install]WantedBy=multi-user.target
Save that and enable it….
$ sudo systemctl daemon-reload$ sudo systemctl enable node-red.service$ sudo systemctl start node-red.service$ sudo systemctl status node-red.service
Save Now you can access the Node-Red on localhost:1880 as 1880 is the default port for
Node-red.
