mosquitto c example 订阅示例
mosquitto有同步和异步两种通讯方式。同步的方式是通信+等待的阻塞模式。
官方手册api地址：https://mosquitto.org/api/files/mosquitto-h.html#mosquitto_connect
有疑问的地方，可以直接看官方手册，比较好懂。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "mosquitto.h"
#define HOST "localhost"
#define PORT 1883
#define KEEP_ALIVE 60
#define MSG_MAX_SIZE 512
// 定义运行标志决定是否需要结束
static int running = 1;
void my_connect_callback(struct mosquitto *mosq, void *obj, int rc)
{
printf("Call the function: on_connect\n");
if(rc){
// 连接错误，退出程序
printf("on_connect error!\n");
exit(1);
}else{
// 订阅主题
// 参数：句柄、id、订阅的主题、qos
if(mosquitto_subscribe(mosq, NULL, "topic1", 2)){
printf("Set the topic error!\n");
exit(1);
}
}
}
void my_disconnect_callback(struct mosquitto *mosq, void *obj, int rc)
{
printf("Call the function: my_disconnect_callback\n");
running = 0;
}
void my_subscribe_callback(struct mosquitto *mosq, void *obj, int mid, int qos_count, const int *granted_qos)
{
printf("Call the function: on_subscribe\n");
}
void my_message_callback(struct mosquitto *mosq, void *obj, const struct mosquitto_message *msg)
{
printf("Call the function: on_message\n");
printf("Recieve a message of %s : %s\n", (char *)msg->topic, (char *)msg->payload);
if(0 == strcmp(msg->payload, "quit")){
mosquitto_disconnect(mosq);
}
}
int main()
{
int ret;
struct mosquitto *mosq;
// 初始化mosquitto库
ret = mosquitto_lib_init();
if(ret){
printf("Init lib error!\n");
return -1;
}
// 创建一个订阅端实例
// 参数：id（不需要则为NULL）、clean_start、用户数据
mosq = mosquitto_new("sub_test", true, NULL);
if(mosq == NULL){
printf("New sub_test error!\n");
mosquitto_lib_cleanup();
return -1;
}
// 设置回调函数
// 参数：句柄、回调函数
mosquitto_connect_callback_set(mosq, my_connect_callback);
mosquitto_disconnect_callback_set(mosq, my_disconnect_callback);
mosquitto_subscribe_callback_set(mosq, my_subscribe_callback);
mosquitto_message_callback_set(mosq, my_message_callback);
// 连接至服务器
// 参数：句柄、ip（host）、端口、心跳
ret = mosquitto_connect(mosq, HOST, PORT, KEEP_ALIVE);
if(ret){
printf("Connect server error!\n");
mosquitto_destroy(mosq);
mosquitto_lib_cleanup();
return -1;
}
// 开始通信：循环执行、直到运行标志running被改变
printf("Start!\n");
while(running)
{
mosquitto_loop(mosq, -1, 1);
}
// 结束后的清理工作
mosquitto_destroy(mosq);
mosquitto_lib_cleanup();
printf("End!\n");
return 0;
}