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Red Hat OpenShift xPaaS - Simple MQTT with OpenShift, Part Two, Simple client connecting to Broker on xPaaS

This demo will be divided into 2 parts, first part is about setting up the Messaging broker on OpenShift with MQTT Connector. Second part we are going to write a simple demo trying to connect to the broker via MQTT.

This is the 2nd part of the demo, we have previously setup a broker on Openshift, the PaaS offering from Red Hat. (see Part One). Now we have a broker running on the cloud ready to service. 

Apart from, MQTT is a very "lightweight " protocol. MQTT's nature act as a publish/subscribe messaging transport, so base on the scenario, it is more suitable for Topic, there will be no queue implementation for MQTT. 

This demo is a very simple producer and consumer, publishing messages through MQTT protocol. Using library of fusesource's mqtt-client. 

Before we start, please make sure you have successfully setup the broker on OpenShift. (see Part One). And we need to setup the environment in our local machine to work with xPaaS. Normally, the port are access on the PaaS itself. If the developer wants to access the broker in their machine, rather then configuring the complex networking setup. Openshift has a simple feature, which simply forward the service port on the PaaS to local machine. To do that , simply run the following command.

rhc port-forward $YOUR_CONTAINER_NAME 






For Mac Users, sometimes you need to add the following command to create an alias on your local machine for the IP address of the OpenShift broker 

sudo ifconfig lo0 alias $OPENSHIFT_IP

To run the demo, please clone the git repo to your local machine by running

git clone https://github.com/weimeilin79/mqtt-demo.git

And run the init.sh to setup. You will need to enter your Broker URL, user name of fuse console and the password. 

./init.sh
  • The broker URL is the mqtt port (default 1883 if you have been following the setup), and the IP will be mapped to your local machine. So it should be 127.0.0.1.
  • The user name of console and the password are given to you from previous setup in openshift. 










To run the consumer and producer, just go to the projects/mqttdemo directory and run 

mvn -P consumer 
mvn -P producer  

it will start sending the messages.  
In the same time you will see the statistics changing on Openshift.

Going through the development part. in pom.xml , remember to add the mqtt-client library. 

   
   
    org.fusesource.mqtt-client
    mqtt-client
    1.11-SNAPSHOT
   
   
    org.fusesource.mqtt-client
    mqtt-client-java1.4-uber
    1.11-SNAPSHOT
   
   
     org.fusesource.hawtbuf
    hawtbuf
    1.9
   
  
As for the producer and consumer, it's just simple API Call. 
(There are many different API to work with, I will show you if I have time.)
MQTT mqtt = new MQTT();
mqtt.setHost(props.getProperty(BROKER_URL));
mqtt.setUserName(props.getProperty(USERNAME));
mqtt.setPassword(props.getProperty(PASSWORD));
  
  
BlockingConnection connection = mqtt.blockingConnection();
connection.connect();
Topic[] topics = {new Topic(utf8("foo"), QoS.AT_LEAST_ONCE)};
connection.subscribe(topics);
Message message = connection.receive();
message.ack();
connection.disconnect();


/////VIDEO COMING SOON///////


Comments

Zachariah Young said…
How do you connect to the MQTT broker without doing the network alias? I'm working on a java program locally and don't want to setup the local network alias.

Thanks

Zach

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