net/mqtt: Add support for IBM BlueMix Watson topic format

Change-Id: I044180d9f76a307c1cf4423a9b1d3ee6c540cbc7
Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>

Author: ldts

samples/net/mqtt_publisher/README.rst

@@ -67,6 +67,12 @@ Max number of MQTT PUBLISH iterations
 
 	#define APP_MAX_ITERATIONS	5
 
+IBM BlueMix IoT Watson topic format
+
+.. code block:: c
+
+	#define ENABLE_BLUEMIX_TOPIC	0
+
 On your Linux host computer, open a terminal window, locate the source code
 of this sample application (i.e. :file:`samples/net/mqtt_publisher`) and type:
 

samples/net/mqtt_publisher/src/config.h

@@ -34,4 +34,6 @@
 
 #define APP_MAX_ITERATIONS	100
 
+#define ENABLE_BLUEMIX_TOPIC	0
+
 #endif

samples/net/mqtt_publisher/src/main.c

@@ -13,6 +13,7 @@
 #include <misc/printk.h>
 #include <string.h>
 #include <errno.h>
+#include <stdio.h>
 
 #if defined(CONFIG_NET_L2_BLUETOOTH)
 #include <bluetooth/bluetooth.h>
@@ -24,6 +25,8 @@
 
 #define CLIENTID "zephyr_publisher"
 
+static bool bluemix_publisher;
+
 /**
  * @brief mqtt_client_ctx	Container of some structures used by the
  *				publisher app.
@@ -176,28 +179,58 @@ void malformed_cb(struct mqtt_ctx *mqtt_ctx, uint16_t pkt_type)
 	printk("[%s:%d] pkt_type: %u\n", __func__, __LINE__, pkt_type);
 }
 
-static const char topic[] = "sensors";
+static
+char *get_payload(enum mqtt_qos qos)
+{
+	static char payload[30];
+
+	if (bluemix_publisher) {
+		snprintf(payload,
+			sizeof(payload),
+			"{d:{temperature:%d}}",
+			(uint8_t) sys_rand32_get());
+	} else {
+		strncpy(payload, "DOORS:OPEN_QoSx", sizeof(payload));
+		payload[strlen(payload) - 1] = '0' + qos;
+	}
 
-char payload[] = "DOORS:OPEN_QoSx";
+	return payload;
+}
 
 static
-void prepare_mqtt_publish_msg(struct mqtt_publish_msg *pub_msg,
-			      enum mqtt_qos qos)
+char *get_topic(void)
 {
-	payload[strlen(payload) - 1] = '0' + qos;
+	static char topic[50];
+
+	if (bluemix_publisher) {
+		snprintf(topic, sizeof(topic),
+			"iot-2/type/%s/id/%s/evt/%s/fmt/%s",
+			"sensor",	/* device type  */
+			"carbon",	/* device id    */
+			"status",	/* event type   */
+			"json");	/* event format */
+	} else {
+		strncpy(topic, "sensors", sizeof(topic));
+	}
 
+	return topic;
+}
+
+static
+void prepare_mqtt_publish_msg(struct mqtt_publish_msg *pub_msg,
+			enum mqtt_qos qos)
+{
 	/* MQTT message payload may be anything, we we use C strings */
-	pub_msg->msg = payload;
+	pub_msg->msg = get_payload(qos);
 	/* Payload's length */
 	pub_msg->msg_len = strlen(client_ctx.pub_msg.msg);
 	/* MQTT Quality of Service */
 	pub_msg->qos = qos;
 	/* Message's topic */
-	pub_msg->topic = (char *)topic;
+	pub_msg->topic = get_topic();
 	pub_msg->topic_len = strlen(client_ctx.pub_msg.topic);
 	/* Packet Identifier, always use different values */
 	pub_msg->pkt_id = sys_rand32_get();
-
 }
 
 #define RC_STR(rc)	((rc) == 0 ? "OK" : "ERROR")
@@ -464,5 +497,9 @@ int network_setup(struct net_context **net_ctx, const char *local_addr,
 
 void main(void)
 {
+
+#if ENABLE_BLUEMIX_TOPIC
+	bluemix_publisher = true;
+#endif
 	publisher();
 }