samples/net/mqtt: Update README file and code cleanup

Add instructions to download Paho's MQTT Library.
Simplify if statement.

Change-Id: Iba500c47a56896f9c9b726751933443a5318ced7
Signed-off-by: Flavio Santes <flavio.santes@intel.com>

samples/net/paho_mqtt_client/README

@@ -1,4 +1,4 @@
-MQTT sample using the Paho's MQTT Packet.
+MQTT sample using the Paho's MQTT Packet Library.
 
 Requirements
 ------------
@@ -25,9 +25,20 @@ Building instructions
   See http://www.eclipse.org/paho/clients/c/embedded/ for more
   information about Paho's MQTT Packet Library.
 
-* Modify the src/Makefile to reflect the location of your Paho
+  Inside samples/net/paho_mqtt_client, run the following commands:
-  repository. In this example, it is assumed that src/paho_mqtt_pkt
+
-  is the directory that contains the MQTTPacket source code.
+  git clone https://git.eclipse.org/r/paho/org.eclipse.paho.mqtt.embedded-c paho
+
+  Now "paho" contains the MQTT Packet Library.
+
+* make pristine && make are enough to build this sample.
+
+* Follow the steps indicated here:
+
+  https://www.zephyrproject.org/doc/board/galileo.html
+
+  to load the binary into the Galileo Dev Board.
+
 
 Usage
 -----

samples/net/paho_mqtt_client/src/main.c

@@ -24,9 +24,9 @@
 #include "mqtt.h"
 
 #define RC_MSG(rc)		(rc) == 0 ? "success" : "failure"
-#define STACKSIZE		1024
+#define STACK_SIZE		1024
 
-uint8_t stack[STACKSIZE];
+uint8_t stack[STACK_SIZE];
 
 struct net_context *ctx;
 
@@ -72,6 +72,6 @@ void main(void)
 	net_init();
 	tcp_init(&ctx);
 
-	task_fiber_start(stack, STACKSIZE, (nano_fiber_entry_t)fiber,
+	task_fiber_start(stack, STACK_SIZE, (nano_fiber_entry_t)fiber,
 			 0, 0, 7, 0);
 }

samples/net/paho_mqtt_client/src/mqtt.c

@@ -18,6 +18,7 @@
 #include <errno.h>
 
 #include "mqtt.h"
+#include "tcp.h"
 
 #include "MQTTPacket.h"
 #include "MQTTConnect.h"
@@ -29,9 +30,6 @@
 #define BUF_SIZE 128
 static uint8_t mqtt_buffer[BUF_SIZE];
 
-
-#include "tcp.h"
-
 int mqtt_connect(struct net_context *ctx, char *client_name)
 {
 	MQTTPacket_connectData data = MQTTPacket_connectData_initializer;
@@ -70,12 +68,8 @@ int mqtt_connect(struct net_context *ctx, char *client_name)
 	}
 	rc = MQTTDeserialize_connack(&session_present, &conn_ack,
 				     mqtt_buffer, rx_len);
-	rc = rc != 1 ? -EINVAL : 0;
-	if (rc != 0) {
-		return -EINVAL;
-	}
 
-	return conn_ack;
+	return rc == 1 ? conn_ack : -EINVAL;
 }
 
 int mqtt_disconnect(struct net_context *ctx)
@@ -157,7 +151,7 @@ int mqtt_pingreq(struct net_context *ctx)
 
 int mqtt_publish_read(struct net_context *ctx)
 {
-	MQTTString received_topic;
+	MQTTString topic;
 	unsigned char dup;
 	unsigned char retained;
 	unsigned short msg_id;
@@ -173,11 +167,13 @@ int mqtt_publish_read(struct net_context *ctx)
 	}
 
 	rc = MQTTDeserialize_publish(&dup, &qos, &retained, &msg_id,
-				     &received_topic, &msg, &msg_len,
+				     &topic, &msg, &msg_len,
 				     mqtt_buffer, rx_len);
 	rc = rc == 1 ? 0 : -EIO;
 	if (rc == 0) {
-		printf("\n\tReceived message: %.*s\n\n", msg_len, msg);
+		printf("\n\tReceived message: [%.*s] %.*s\n\n",
+		       topic.lenstring.len, topic.lenstring.data,
+		       msg_len, msg);
 	}
 	return rc;
 }
@@ -214,6 +210,6 @@ int mqtt_subscribe(struct net_context *ctx, char *topic)
 	rc = MQTTDeserialize_suback(&submsg_id, 1, &sub_count, &granted_qos,
 				    mqtt_buffer, rx_len);
 
-	return rc != 1 ?  -EINVAL : granted_qos;
+	return rc == 1 ? granted_qos : -EINVAL;
 }
 

samples/net/paho_mqtt_client/src/tcp.h

@@ -23,5 +23,4 @@ int tcp_init(struct net_context **ctx);
 int tcp_tx(struct net_context *ctx, uint8_t *buf,  size_t size);
 int tcp_rx(struct net_context *ctx, uint8_t *buf, size_t *read_bytes, size_t size);
 
-
 #endif