Add pubsub client

libraries/PubSubClient/examples/mqtt_basic/mqtt_basic.ino

@@ -0,0 +1,38 @@
+/*
+ Basic MQTT example 
+ 
+  - connects to an MQTT server
+  - publishes "hello world" to the topic "outTopic"
+  - subscribes to the topic "inTopic"
+*/
+
+#include <SPI.h>
+#include <Ethernet.h>
+#include <PubSubClient.h>
+
+// Update these with values suitable for your network.
+byte mac[]    = {  0xDE, 0xED, 0xBA, 0xFE, 0xFE, 0xED };
+byte server[] = { 172, 16, 0, 2 };
+byte ip[]     = { 172, 16, 0, 100 };
+
+void callback(char* topic, byte* payload, unsigned int length) {
+  // handle message arrived
+}
+
+EthernetClient ethClient;
+PubSubClient client(server, 1883, callback, ethClient);
+
+void setup()
+{
+  Ethernet.begin(mac, ip);
+  if (client.connect("arduinoClient")) {
+    client.publish("outTopic","hello world");
+    client.subscribe("inTopic");
+  }
+}
+
+void loop()
+{
+  client.loop();
+}
+