Simple example of MQTT message publishing using Clojure and the Eclipse Paho libraries

mqtt.clj

;; Simple example of MQTT message publish using Clojure
;;
;; Uses the Websphere Eclipse Paho client
;; 
;; Author:   Frederico Munoz <[email protected]>
;; Date:     18-Jun-2013
;; Keywords: mqtt, messaging, m2m, telemetry, clojure, iot, paho
;;
;; Copying and distribution of this file, with or without modification,
;; are permitted in any medium without royalty provided the copyright
;; notice and this notice are preserved.  This file is offered as-is,
;; without any warranty.
;;
;; See http://www.eclipse.org/paho/ for the Eclipse Paho
;; implementation of MQTT, including the
;; org.eclipse.paho.client.mqttv3.jar JAR file which is used in this
;; example and should be in the classpath.
;;
;; Use of leiningen is recommended for any more advanced use, but
;; assuming all the jars are in the current directory the following
;; should work:
;;
;; $ java -cp clojure.jar:org.eclipse.paho.client.mqttv3.jar clojure.main mqtt.clj
;; Sat Jun 22 17:53:49 WEST 2013 : Sent 
;; Connected to  tcp://m2m.eclipse.org:1883
;; *** PUBLISHING TO TOPIC  cljtest  ***
;; *** DELIVERY COMPLETE ***
;; $
;;
;; This code only shows how to publish, but there are several MQTT
;; clients that can be used to subscribe to the topic. The Mosquitto
;; MQTT implementation (http://mosquitto.org/) comes with a client
;; which can be used thus:
;;
;; $ mosquitto_sub -h m2m.eclipse.org -t "cljtest" -v
;; cljtest But at least, out of my bitterness at what I'll never be, There's the quick calligraphy of these lines, The broken archway to the Impossible.
;; ^C
;; $

(import 'org.eclipse.paho.client.mqttv3.MqttCallback)
(import 'org.eclipse.paho.client.mqttv3.MqttClient)
(import 'org.eclipse.paho.client.mqttv3.MqttConnectOptions)
(import 'org.eclipse.paho.client.mqttv3.MqttDeliveryToken)
(import 'org.eclipse.paho.client.mqttv3.MqttException)
(import 'org.eclipse.paho.client.mqttv3.MqttMessage)
(import 'org.eclipse.paho.client.mqttv3.MqttTopic)

;; Main variables, most likely candidates for additional command line arguments
;; Change them according to your environment (the message can be supplied in the cli)
(def broker-url "tcp://m2m.eclipse.org:1883") ; Eclipse sandbox server, see http://m2m.eclipse.org/sandbox.html for details on use
(def mqtt-topic-name "cljtest")
(def mqtt-message (if (seq (first *command-line-args*))   ; Message, either the first 
                    (first *command-line-args*)           ; command line argument or a snippet from Tobacco Shop
                    "But at least, out of my bitterness at what I'll never be, There's the quick calligraphy of these lines, The broken archway to the Impossible."))
(def client-id "FSM-Clj-Test")

(defn- mqtt-callback 
  "Function called after delivery confirmation"
  []
  (reify MqttCallback 
    (connectionLost [_ cause]
      (println (.toString cause)))
    (messageArrived [_ topic message]
      (println "Topic: " (.getName topic))
      (println "Message: " (.getPayload message)))
    (deliveryComplete [_ token]
      (println "*** DELIVERY COMPLETE ***"))))

(defn- mqtt-connect
  "Establishes a MQTT connection to TOPIC; returns the mqtt client object"
  [topic]
  (let [mqtt-conn-options (MqttConnectOptions.)
        mqtt-client (MqttClient. broker-url client-id)]
    (doto mqtt-conn-options
      (.setCleanSession 'true)
      (.setKeepAliveInterval 30))
    (println "Connected to " broker-url)
    (.setCallback mqtt-client (mqtt-callback))
    (.connect mqtt-client mqtt-conn-options)
    mqtt-client))

(defn- mqtt-create-message
  "Creates a MQTT message from MESSAGE, a string"
  [message]
  (let [mqtt-message (MqttMessage. (.getBytes message))]
    (doto mqtt-message
      (.setQos  0)
      (.setRetained false))))

(defn- mqtt-publish 
  "Publishes MESSAGE to TOPIC"
  [topic message]
  (println "*** PUBLISHING TO TOPIC " (.toString topic) " ***")
  (.waitForCompletion (.publish topic message)))

(defn testmq 
  "Main demo function, creates the connection and sends the message"
  []
  (let [client (mqtt-connect mqtt-topic-name)
        topic (.getTopic client mqtt-topic-name)
        message (mqtt-create-message mqtt-message)]
    (mqtt-publish topic message)
    (Thread/sleep 100)
    (.disconnect client)
    (shutdown-agents)))

;; Make it all work
(testmq)

;; End of file