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mqtt.lua

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+-- Configuration to connect to the MQTT broker.
+BROKER = "172.16.2.15"   -- Ip/hostname of MQTT broker
+BRPORT = 1883             -- MQTT broker port
+BRUSER = ""           -- If MQTT authenitcation is used then define the user
+BRPWD  = ""            -- The above user password
+CLIENTID = "ESP8266-" ..  node.chipid() -- The MQTT ID. Change to something you like
+
+SWITCH_PIN = 0
+
+SWITCH_ID = 0
+
+-- MQTT topics to subscribe
+topics = {"IoT/Watchdog", "IoT/Switch" .. SWITCH_ID} -- Add/remove topics to the array
+
+-- Control variables.
+pub_sem = 0         -- MQTT Publish semaphore. Stops the publishing whne the previous hasn't ended
+current_topic  = 1  -- variable for one currently being subscribed to
+topicsub_delay = 50 -- microseconds between subscription attempts, worked for me (local network) down to 5...YMMV
+id1 = 0
+id2 = 0
+
+switch_state = 0
+
+
+gpio.mode(SWITCH_PIN, gpio.OUTPUT)
+gpio.write(SWITCH_PIN, gpio.LOW)
+
+-- connect to the broker
+print "Connecting to MQTT broker. Please wait..."
+m = mqtt.Client( CLIENTID, 120, BRUSER, BRPWD)
+m:connect( BROKER , BRPORT, 0, function(conn)
+     print("Connected to MQTT:" .. BROKER .. ":" .. BRPORT .." as " .. CLIENTID )
+     mqtt_sub() --run the subscription function
+end)
+
+function mqtt_sub()
+     if table.getn(topics) < current_topic then
+          -- if we have subscribed to all topics in the array, run the main prog
+          run_main_prog()
+     else
+          --subscribe to the topic
+          m:subscribe(topics[current_topic] , 0, function(conn)
+               print("Subscribing topic: " .. topics[current_topic - 1] )
+          end)
+          current_topic = current_topic + 1  -- Goto next topic
+          --set the timer to rerun the loop as long there is topics to subscribe
+          tmr.alarm(5, topicsub_delay, 0, mqtt_sub )
+     end
+end
+
+-- Sample publish functions:
+function publish_heartbeat()
+   if pub_sem == 0 then  -- Is the semaphore set=
+     pub_sem = 1  -- Nop. Let's block it
+     local uptime = tmr.time()
+     local msg = "{\"metadata\":{\"device\":\"WiFiSwitch" .. SWITCH_ID .. "\"}, \"data\":{\"uptime\":" .. uptime .. "}}"
+     m:publish("IoT/Heartbeat/WiFiSwitch" .. SWITCH_ID, msg ,0,0, function(conn) 
+        -- Callback function. We've sent the data
+        print("Heartbeat sent: " .. id1)
+        pub_sem = 0  -- Unblock the semaphore
+        id1 = id1 +1 -- Let's increase our counter
+     end)
+   end  
+end
+
+function publish_status()
+   if pub_sem == 0 then  -- Is the semaphore set=
+     pub_sem = 1  -- Nop. Let's block it
+     local uptime = tmr.time()
+     local msg = "{\"metadata\":{\"device\":\"WiFiSwitch" .. SWITCH_ID .. "\"}, \"data\":{\"uptime\":" .. uptime .. ", \"state\":" .. switch_state .. "}}"
+     m:publish("IoT/Status/WiFiSwitch" .. SWITCH_ID, msg ,0,0, function(conn) 
+        -- Callback function. We've sent the data
+        print("Status sent: " .. id2)
+        print("State: " .. switch_state)
+        pub_sem = 0  -- Unblock the semaphore
+        id2 = id2 +1 -- Let's increase our counter
+     end)
+   end  
+end
+
+
+
+--main program to run after the subscriptions are done
+function run_main_prog()
+     print("Main program")
+     
+     tmr.alarm(2, 1000, 1, publish_heartbeat )
+     tmr.alarm(3, 1346, 1, publish_status )
+     -- Callback to receive the subscribed topic messages. 
+     m:on("message", function(conn, topic, data)
+        print(topic .. ":" )
+        if (data ~= nil ) then
+          print ( data )
+          if (data == "switch on") then
+            switch_state = 1
+            gpio.write(SWITCH_PIN, gpio.HIGH)
+          elseif (data == "switch off") then
+            switch_state = 0
+            gpio.write(SWITCH_PIN, gpio.LOW)
+          end
+        end
+      end )
+end
+