【MQTT编程】消息Publish实践：Synchronous publication同步发布示例

旧城等待， 2022-11-11 14:41 98阅读 0赞

**编程框架**

> Using the client  
> **Applications that use the client library typically use a similar structure:**  
> **1**）Create a client object  
> **2**）Set the options to connect to an MQTT server  
> **3**）Set up callback functions if multi-threaded (asynchronous mode) operation is being used (see Asynchronous vs synchronous client applications).  
> **4**）Subscribe to any topics the client needs to receive  
> **5**）Repeat until finished:  
> Publish any messages the client needs to  
> Handle any incoming messages  
> **6**）Disconnect the client  
> **7**）Free any memory being used by the client

#include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <unistd.h>
    #include "MQTTClient.h"
    #define ADDRESS     "tcp://192.168.1.101:1883"
    #define CLIENTID    "ExampleClientPub"
    #define TOPIC       "MQTT_Examples"
    #define PAYLOAD     "Hello MQTT!"
    #define QOS         1
    #define TIMEOUT     10000L
    
    int main(int argc, char* argv[])
    {
        
        MQTTClient client;
        MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
        MQTTClient_message pubmsg = MQTTClient_message_initializer;
        MQTTClient_deliveryToken token;
        int rc;
        MQTTClient_create(&client, ADDRESS, CLIENTID,
            MQTTCLIENT_PERSISTENCE_NONE, NULL);
        conn_opts.keepAliveInterval = 20;
        conn_opts.cleansession = 1;
        if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
        {
        
            printf("Failed to connect, return code %d\n", rc);
            exit(EXIT_FAILURE);
        }
        pubmsg.payload = PAYLOAD;
        pubmsg.payloadlen = strlen(PAYLOAD);
        pubmsg.qos = QOS;
        pubmsg.retained = 0;
        while (1)
        {
        
            MQTTClient_publishMessage(client, TOPIC, &pubmsg, &token);
            printf("Waiting for up to %d seconds for publication of %s\n"
                    "on topic %s for client with ClientID: %s\n",
                    (int)(TIMEOUT/1000), PAYLOAD, TOPIC, CLIENTID);
            rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);
            printf("Message with delivery token %d delivered\n", token);
            sleep(1);
        }
        
        MQTTClient_disconnect(client, 10000);
        MQTTClient_destroy(&client);
        return rc;
    }