Implementation of C language-based client mosquitto of MQTT

In the process of learning about the content MQTT in me has helped
https://www.runoob.com/w3cnote/mqtt-intro.html entry-level introduction to the very foundation of MQTT explain what is MQTT
HTTPS: // mosquitto .org / api / files / mosquitto- h.html the site recorded almost all of mosquitto interface you want to know he has a function interface function Introduction may not see any point to look into the detailed explanation is very clear

The following pictures can explain more intuitive communication protocol MQTT

According to these two pictures talk about my understanding of MQTT of:
running the broker is the real servers that governs publish and subscribe messages in all MQTT agreement and his client may have about triple the case
1. Run the publisher of the program of work doing publish
2. run the subscriber's program of work doing subscribe
3. run the subscriber and the publisher can publish both programs can also subscribe this does not mean that such a program is to broker
these three cases you you can determine your own client according to their actual needs which can be
, for example, your clients just need to receive from the broker's topic is "ycy" message and then parsing process does not need to do any work then you publish you can choose the first two kinds of clients

My program's function is to process the message began to get treatment after a fixed topic of messages from the cloud after the completion publish because I go out I have to do an imitation of the broker on a Linux machine to achieve this step to get the message from the clouds

First of all I expected was this

But this will lead every time I publish data out of my own will receive a copy so I will scan the data again to determine the character needs to resolve the situation is not exactly the process in case of agreement to parse (which big misunderstanding)
so do not use the same topic in fact, there are two solutions (hereinafter say to me here)

Solution two:
is the filter in my_message_callback this function at their publish a topic filter what (in my code below and did not realize just provide ideas strcmp function can help a lot)

mqtt_server.c

#include <stdio.h>
#include <stdlib.h>
#include <mosquitto.h>
#include <string.h>

#define HOST "localhost"
#define PORT  1883
#define KEEP_ALIVE 60
#define MSG_MAX_SIZE  512
#define TOPIC_NUM 3

bool session = true;

const static char* topic[TOPIC_NUM] =
{
    "Gai爷:",
    "ycy ",
    "CCYY "
};

void my_message_callback(struct mosquitto *mosq, void *userdata, const struct mosquitto_message *message)
{
    
    if(message->payloadlen){
        printf("%s %s", message->topic, (char *)message->payload);
    }else{
        printf("%s (null)\n", message->topic);
    }
    fflush(stdout);
}

void my_connect_callback(struct mosquitto *mosq, void *userdata, int result)
{
    int i;
    if(!result){
        /* Subscribe to broker information topics on successful connect. */
        mosquitto_subscribe(mosq, NULL, "CCYY ", 2);
    }else{
        fprintf(stderr, "Connect failed\n");
    }
}

void my_subscribe_callback(struct mosquitto *mosq, void *userdata, int mid, int qos_count, const int *granted_qos)
{
    int i;
    printf("Subscribed (mid: %d): %d", mid, granted_qos[0]);
    for(i=1; i<qos_count; i++){
        printf(", %d", granted_qos[i]);
    }
    printf("\n");
}

void my_log_callback(struct mosquitto *mosq, void *userdata, int level, const char *str)
{
    /* Pring all log messages regardless of level. */
    printf("%s\n", str);
}

int main()
{
    struct mosquitto *mosq = NULL;
    char buff[MSG_MAX_SIZE];
    
    //libmosquitto 库初始化
    mosquitto_lib_init();
    //创建mosquitto客户端
    mosq = mosquitto_new(NULL,session,NULL);
    if(!mosq){
        printf("create client failed..\n");
        mosquitto_lib_cleanup();
        return 1;
    }
    //设置回调函数，需要时可使用
    mosquitto_log_callback_set(mosq, my_log_callback);
    mosquitto_connect_callback_set(mosq, my_connect_callback);
    mosquitto_message_callback_set(mosq, my_message_callback);
    mosquitto_subscribe_callback_set(mosq, my_subscribe_callback);
    

    //连接服务器
    if(mosquitto_connect(mosq, HOST, PORT, KEEP_ALIVE)){
        fprintf(stderr, "Unable to connect.\n");
        return 1;
    }
    //开启一个线程，在线程里不停的调用 mosquitto_loop() 来处理网络信息
    int loop = mosquitto_loop_start(mosq); 
    if(loop != MOSQ_ERR_SUCCESS)
    {
        printf("mosquitto loop error\n");
        return 1;
    }


    while(fgets(buff, MSG_MAX_SIZE, stdin) != NULL)
    {
        /*发布消息*/
        mosquitto_publish(mosq,NULL,"ycy ",strlen(buff)+1,buff,0,0);
        memset(buff,0,sizeof(buff));
    }

    mosquitto_destroy(mosq);
    mosquitto_lib_cleanup();

    return 0;
}

mqtt_client.c

#include <stdio.h>
#include <stdlib.h>
#include <mosquitto.h>
#include <string.h>

#define HOST "localhost"
#define PORT  1883
#define KEEP_ALIVE 60
#define MSG_MAX_SIZE  512
#define TOPIC_NUM 3

bool session = true;

const static char* topic[TOPIC_NUM] =
{
    "Gai爷:",
    "ycy ",
    "CCYY "
};

void my_message_callback(struct mosquitto *mosq, void *userdata, const struct mosquitto_message *message)
{
    
    if(message->payloadlen){
        printf("%s %s", message->topic, (char *)message->payload);
    }else{
        printf("%s (null)\n", message->topic);
    }
    fflush(stdout);
}

void my_connect_callback(struct mosquitto *mosq, void *userdata, int result)
{
    int i;
    if(!result){
        /* Subscribe to broker information topics on successful connect. */
        mosquitto_subscribe(mosq, NULL, "ycy ", 2);
    }else{
        fprintf(stderr, "Connect failed\n");
    }
}

void my_subscribe_callback(struct mosquitto *mosq, void *userdata, int mid, int qos_count, const int *granted_qos)
{
    int i;
    printf("Subscribed (mid: %d): %d", mid, granted_qos[0]);
    for(i=1; i<qos_count; i++){
        printf(", %d", granted_qos[i]);
    }
    printf("\n");
}

void my_log_callback(struct mosquitto *mosq, void *userdata, int level, const char *str)
{
    /* Pring all log messages regardless of level. */
    printf("%s\n", str);
}

int main()
{
    struct mosquitto *mosq = NULL;
    char buff[MSG_MAX_SIZE];
    
    //libmosquitto 库初始化
    mosquitto_lib_init();
    //创建mosquitto客户端
    mosq = mosquitto_new(NULL,session,NULL);
    if(!mosq){
        printf("create client failed..\n");
        mosquitto_lib_cleanup();
        return 1;
    }
    //设置回调函数，需要时可使用
    mosquitto_log_callback_set(mosq, my_log_callback);
    mosquitto_connect_callback_set(mosq, my_connect_callback);
    mosquitto_message_callback_set(mosq, my_message_callback);
    mosquitto_subscribe_callback_set(mosq, my_subscribe_callback);
    

    //连接服务器
    if(mosquitto_connect(mosq, HOST, PORT, KEEP_ALIVE)){
        fprintf(stderr, "Unable to connect.\n");
        return 1;
    }
    //开启一个线程，在线程里不停的调用 mosquitto_loop() 来处理网络信息
    int loop = mosquitto_loop_start(mosq); 
    if(loop != MOSQ_ERR_SUCCESS)
    {
        printf("mosquitto loop error\n");
        return 1;
    }


    while(fgets(buff, MSG_MAX_SIZE, stdin) != NULL)
    {
        /*发布消息*/
        mosquitto_publish(mosq,NULL,"CCYY ",strlen(buff)+1,buff,0,0);
        memset(buff,0,sizeof(buff));
    }

    mosquitto_destroy(mosq);
    mosquitto_lib_cleanup();

    return 0;
}

makefile

#不是系统默认库 要记得添加连接选项

all:Client
    @echo ""
    @echo "Start compiling......"
    @echo ""
Client:Server
    gcc -o Client mqtt_client.c -lmosquitto -lpthread

Server:
    gcc -o Server mqtt_server.c -lmosquitto -lpthread

clean:
    -rm Server Client

Screenshot program runs as follows:

Server

Client

the above