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How the Publisher Send Message to the Server in MQTT Contiki Cooja?

The publisher send message to server in MQTT contiki cooja

Contiki cooja steps for the publisher to send message to the server in MQTT

Description:

   Sender of the messages is called publisher in pub/sub pattern. Publish the topics periodically and also know about how to send the publish message to server in MQTT contiki cooja simulator.

Source code

Step 1: Open a file at location:contiki/ mqtt-sn-contiki/main_core.c
Define topics like this,
static char *topics_mqtt[] = {“/topic_1”, “/topic_2”, “/topic_3″”/topic_4”, “/topic_5”, “/topic_6”};

Step 2: Create socket to publish
mqtt_sn_init(); // initiation
size_t i;
for(i=0;i<ss(topics_mqtt);i++)
all_topics[i] = topics_mqtt[i];
all_topics[i] = topic_hw;
mqtt_sn_create_sck(mqtt_sn_connection,all_topics,ss(all_topics),mqtt_sn_callback);

Step 3: initiate broker and publish the message periodically
while(1) {
PROCESS_WAIT_EVENT();
sprintf(pub_test,”%s”,topic_hw);
mqtt_sn_pub(“/topic_1”,pub_test,true,0);
if (etimer_expired(&time_poll))
etimer_reset(&time_poll);
}

Step 4: contiki/ mqtt-sn-contiki/mqtt_sn.c
resp_con_t mqtt_sn_pub_send(char *topic, char *message, bool retain_flag, uint8_t qos). handles publish message to broker.

Step 5: Open cooja simulator

Run simulation

Run simulation
Output
Result of the cooja simulator Publisher send the message to server