MQTT? MQ Telemetry Transport - "a machine-to-machine (M2M)/"Internet of Things" connectivity protocol".
RSMB? Really Small Message Broker - "a very small messaging server that uses the lightweight MQTT publish/subscribe protocol to distribute messages between applications".
So what do I want to do with this stuff? Well, you will now know that I got myself a Raspberry Pi and I was scratching around thinking of things I'd like my Pi to do. I came across an excellent video showing how Andy Stanford-Clark is utilising his Pi to monitor and control devices around his home - it is definitely worth a look
I have no intention (yet) of trying to copy Andy's achievements as I'm quite sure I don't have the spare hours in the day! However, I was intrigued to see if I could use my favourite tool (TDI) to ping messages to RSMB using MQTT.
Step 1 - Download RSMB
https://www14.software.ibm.com/webapp/iwm/web/preLogin.do?source=AW-0U9
Step 2 - Startup RSMB
Step 3 - Fire up a Subscriber listening to the TDI topic
Step 4 - Write an Assembly Line to use the MQTT Publisher Connector
Step 5 - Populate the output map of my connector and run the Assembly Line.
The result will be a message published to RSMB which I can see in my subscriber utility:
I can also see the RSMB log shows the connections to the server:
Of course, TDI doesn't have an MQTT Publisher Connector - I had to write one. The good news is that this was possibly the simplest connector of all-time to write. That said, it is extra-ordinarily basic and is missing a myriad of features. For example - it does not support authentication to RSMB. It's error handling is what I can only describe as flaky. It is a publisher only - I haven't provided subscriber functions within the connector. But it shows how TDI could be used to ping very simple lightweight messages to a message broker using MQTT.
So what? Sounds like an intellectual exercise, right? Well, maybe. But MQTT is a great way of pushing information to mobile devices (as demonstrated by Dale Lane) so what I have is a means of publishing information from my running assembly lines to multiple mobile devices in real-time - potentially.
At this point, though, it is worth pointing out that the development of a connector is complete overkill for this exercise (though it does look pretty).
Dropping the wmqtt.jar file that can be found in the IA92 package into {TDI_HOME}/jars/3rdparty will allow you to publish to RSMB using the following few lines of TDI scripting:
// Let's create a MQTT client instance
var mqttpersistence = null;
var mqttclient = Packages.com.ibm.mqtt.MqttClient.createMqttClient("tcp://rsmb-server:1883", mqttpersistence);
// Let's connect to the RSMB server and provide a ClientID
var mqttclientid = "tdi-server";
var mqttcleanstart = true;
var mqttkeepalive = 0;
mqttclient.connect(mqttclientid, mqttcleanstart, mqttkeepalive);
// Let's publish
var mqtttopic = "TDI";
var mqttmessage = "This is a sample message!";
var mqttqos = 0;
var mqttretained = false;
mqttclient.publish(mqtttopic, mqttmessage.getBytes("ISO-8859-1"), mqttqos, mqttretained);
var mqttpersistence = null;
var mqttclient = Packages.com.ibm.mqtt.MqttClient.createMqttClient("tcp://rsmb-server:1883", mqttpersistence);
// Let's connect to the RSMB server and provide a ClientID
var mqttclientid = "tdi-server";
var mqttcleanstart = true;
var mqttkeepalive = 0;
mqttclient.connect(mqttclientid, mqttcleanstart, mqttkeepalive);
// Let's publish
var mqtttopic = "TDI";
var mqttmessage = "This is a sample message!";
var mqttqos = 0;
var mqttretained = false;
mqttclient.publish(mqtttopic, mqttmessage.getBytes("ISO-8859-1"), mqttqos, mqttretained);
Not very complicated. In fact, very simple indeed! (The connector I developed doesn't get very much more complicated than this!)
