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本篇内容主要讲解“MQTT如何连接阿里云订阅主题”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“MQTT如何连接阿里云订阅主题”吧!
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cm_main.c文件里面的cm_main_task是主函数,在主函数里面调用cm_test_aliyun函数。
cm_test_aliyun函数：
void cm_test_aliyun(){
cm_printf("[ALIYUN]: aliyun demo start\n");
void *pclient = NULL;
int res = 0;
int rpc_res = 0;
int loop_cnt = 0;
iotx_mqtt_param_t mqtt_params;
HAL_GetProductKey(DEMO_PRODUCT_KEY);
HAL_GetDeviceName(DEMO_DEVICE_NAME);
HAL_GetDeviceSecret(DEMO_DEVICE_SECRET);
memset(&mqtt_params, 0x0, sizeof(mqtt_params));
mqtt_params.handle_event.h_fp = example_event_handle;
pclient = IOT_MQTT_Construct(&mqtt_params);
if (NULL == pclient) {
cm_printf("[ALIYUN]: MQTT construct failed\n");
return -1;
}
res = example_subscribe(pclient); //调用example_subscribe函数
if (res < 0) {
IOT_MQTT_Destroy(&pclient);
return -1;
}
while (1) {
if (0 == loop_cnt % 20) {
example_publish(pclient);
}
IOT_MQTT_Yield(pclient, 200);
loop_cnt += 1;
if(loop_cnt >= 100) {
//break;
}
}
cm_printf("[ALIYUN]: aliyun demo end\n");
}example_subscribe函数：
example_subscribe一开始进行字符串连接，把${YourProductKey}/${YourDeviceName}/user/get拼接出来，然后调用IOT_MQTT_Subscribe函数订阅topic
int example_subscribe(void *handle){
int res = 0;
const char *fmt = "/%s/%s/user/get"; //订阅的MQTT路径
char *topic = NULL;
int topic_len = 0;
topic_len = strlen(fmt) + strlen(DEMO_PRODUCT_KEY) + strlen(DEMO_DEVICE_NAME) + 1;
topic = HAL_Malloc(topic_len);
if (topic == NULL) {
cm_printf("[ALIYUN]: memory not enough\n");
return -1;
}
memset(topic, 0, topic_len);
HAL_Snprintf(topic, topic_len, fmt, DEMO_PRODUCT_KEY, DEMO_DEVICE_NAME);
//通过HAL_Snprintf函数的拼接得出最终的MQTT路径
//示例：${YourProductKey}/${YourDeviceName}/user/get
//其中的：example_message_arrive函数为接收的数据的回调函数
res = IOT_MQTT_Subscribe(handle, topic, IOTX_MQTT_QOS0, example_message_arrive, NULL);
if (res < 0) {
cm_printf("[ALIYUN]: subscribe failed\n");
HAL_Free(topic);
return -1;
}
HAL_Free(topic);
return 0;
}example_message_arrive函数
example_subscribe为topic接收回调函数，当接收到此topic的数据时会放到这里处理
void example_message_arrive(void *pcontext, void *pclient, iotx_mqtt_event_msg_pt msg){
iotx_mqtt_topic_info_t *topic_info = (iotx_mqtt_topic_info_pt) msg->msg;
cm_printf("example_message_arrive \n");
switch (msg->event_type) {
case IOTX_MQTT_EVENT_PUBLISH_RECEIVED:
/* print topic name and topic message */
cm_printf("[ALIYUN]: Message Arrived:");
cm_printf("Topic : %.*s", topic_info->topic_len, topic_info->ptopic);
cm_printf("Payload: %.*s", topic_info->payload_len, topic_info->payload);
cm_printf("\n");
// topic_info->payload为接收到的数据
if(strcmp(topic_info->payload,"1") == 0){
cm_printf("开灯\n");
cm_gpio_write(21,CM_GPIO_LOW);
}else{
cm_printf("关灯\n");
cm_gpio_write(21,CM_GPIO_HIGH);
}
break;
default:
break;
}
}前端通过传入lightState来控制GPIO21是高电平还是低电平
@GetMapping(path="hello")
public WebResult setGPIOState(int lightState){
// XXXXXX：ProductKey
// YYYYYY: 设备名称
PubRequest request = new PubRequest();
request.setProductKey("XXXXXXXXXXXX");
request.setMessageContent(Base64.encodeBase64String((Integer.toString(lightState)).getBytes()));
request.setTopicFullName("/XXXXXXXXXX/YYYYYYYYYYY/user/get");
request.setQos(0); //目前支持QoS0和QoS1。
try {
PubResponse response = defaultAcsClient.getAcsResponse(request);
//System.out.println(response.getSuccess());
//System.out.println(response.getErrorMessage());
} catch (ServerException e) {
e.printStackTrace();
} catch (ClientException e) {
e.printStackTrace();
}
return WebResult.success(1,"hello");
}