mqtt的各种客户端例程

# RT-Thread 连接 EMQ X Cloud with TLS/SSL 本文将使用[RT-Thread](https://www.rt-thread.org/)配合[ART-Pi](https://github.com/RT-Thread-Studio/sdk-bsp-stm32h750-realthread-artpi)搭建MQTT客户端，快速接入[EMQ X Cloud](https://www.emqx.com/zh/cloud) 。 ## EMQ X Cloud简介 [EMQ X Cloud](https://www.emqx.com/zh/cloud) 是由 [EMQ](https://www.emqx.com/zh) 公司推出的可连接海量物联网设备，集成各类数据库及业务系统的全托管云原生 MQTT 服务。作为**全球首个全托管的** [**MQTT 5.0**](https://links.jianshu.com/go?to=https%3A%2F%2Fwww.emqx.com%2Fzh%2Fmqtt%2Fmqtt5) **公有云服务**，EMQ X Cloud 提供了一站式运维代管、独有隔离环境的 MQTT 消息服务。 在万物互联的时代，EMQ X Cloud 可以帮助用户快速构建面向物联网领域的行业应用，轻松实现物联网数据的采集、传输、计算和持久化。<img src="./snapshots/b7f3e53a4f6a789c698e5af8476d3e51.png" alt="b7f3e53a4f6a789c698e5af8476d3e51" style="zoom:80%;" /> 借助云服务商提供的基础计算设施，EMQ X Cloud 面向全球数十个国家与地区提供服务，为 5G 与万物互联应用提供低成本、安全可靠的云服务。 ## 创建和部署EMQ X Cloud 通过[**快速入门**](https://docs.emqx.cn/cloud/latest/quick_start/introduction.html)创建部署[EMQX Cloud](https://docs.emqx.cn/cloud/latest/) 以下是创建完成的实例 - 基础版  - 专业版  - **TLS/SSL** 配置可参考 https://docs.emqx.cn/cloud/latest/deployments/tls_ssl.html ## 创建项目工程 本文使用[RT-Thread](https://www.rt-thread.org/)官方IDE [RT-Thread-Studio](https://www.rt-thread.org/page/studio.html)来创建工程； > 本次Demo使用的是RT-Thread官方的开发板 ART-Pi，通过板载Wifi模块进行联网，可以直接创建一个art_pi_wifi样例工程进行MQTT客户端的开发； <img src="./snapshots/image-20210812113252985.png" alt="image-20210812113252985" style="zoom:80%;" /> ## 工程配置和引入依赖包 1. 进入配置页面<br><br>选择“More”<br> 2. 启用RTC驱动<br> 3. 引入MQTT依赖包<br>启动TLS需设置mqtt线程栈大小 ≥ 6144 4. 配置mbedtls 1. 若选择**用户CA**证书(单/双向认证)<br>  2. 若选择无证书SSL连接(单向认证)<br> 5. 保存当前配置，IDE会将配置更新到工程中<br> 6. 修改宏 **MEMP_NUM_NETDB** 为 **2** <br>位于项目路径"rt-thread\components\net\lwip-2.0.2\src\include\lwip\opt.h:488"<br> ```c /** * MEMP_NUM_NETDB: the number of concurrently running lwip_addrinfo() calls * (before freeing the corresponding memory using lwip_freeaddrinfo()). */ #if !defined MEMP_NUM_NETDB || defined __DOXYGEN__ #define MEMP_NUM_NETDB 2 #endif ``` ## 代码编写 1. 打开**applications/main.c**,可见RT-Thread-Studio已经帮我们生成好了连接WiFi和LED操作的代码<br> ```c #include <rtthread.h> #include <rtdevice.h> #include "drv_common.h" #define LED_PIN GET_PIN(I, 8) extern void wlan_autoconnect_init(void); int main(void) { rt_uint32_t count = 1; rt_pin_mode(LED_PIN, PIN_MODE_OUTPUT); /* init Wi-Fi auto connect feature */ wlan_autoconnect_init(); /* enable auto reconnect on WLAN device */ rt_wlan_config_autoreconnect(RT_TRUE); while(count++) { rt_thread_mdelay(500); rt_pin_write(LED_PIN, PIN_HIGH); rt_thread_mdelay(500); rt_pin_write(LED_PIN, PIN_LOW); } return RT_EOK; } #include "stm32h7xx.h" static int vtor_config(void) { /* Vector Table Relocation in Internal QSPI_FLASH */ SCB->VTOR = QSPI_BASE; return 0; } INIT_BOARD_EXPORT(vtor_config); ``` 2. 为了实现第一次启动也能自动连接WiFi，我们可以在main()加入连接函数；<br> ```c rt_wlan_connect(WIFI_SSID, WIFI_PASSWORD); ``` 3. 分别新建mqtt-client.c和mqtt-client.h;<br>创建mqtt client<br> ```c static void mqtt_create(void) { /* init condata param by using MQTTPacket_connectData_initializer */ MQTTPacket_connectData condata = MQTTPacket_connectData_initializer; static char client_id[50] = { 0 }; rt_memset(&client, 0, sizeof(MQTTClient)); /* config MQTT context param */ { client.uri = MQTT_BROKER_URI; /* config connect param */ memcpy(&client.condata, &condata, sizeof(condata)); rt_snprintf(client_id, sizeof(client_id), "%s%d",MQTT_CLIENTID, rt_tick_get()); client.condata.clientID.cstring = client_id; client.condata.keepAliveInterval = 60; client.condata.cleansession = 1; client.condata.username.cstring = MQTT_USERNAME; client.condata.password.cstring = MQTT_PASSWORD; /* config MQTT will param. */ client.condata.willFlag = 1; client.condata.will.qos = MQTT_QOS; client.condata.will.retained = 0; client.condata.will.topicName.cstring = MQTT_PUBTOPIC; client.condata.will.message.cstring = MQTT_WILLMSG; /* malloc buffer. */ client.buf_size = client.readbuf_size = MQTT_PUB_SUB_BUF_SIZE; client.buf = rt_malloc(client.buf_size); client.readbuf = rt_malloc(client.readbuf_size); if (!(client.buf && client.readbuf)) { rt_kprintf("no memory for MQTT client buffer!\n"); goto _exit; } /* set event callback function */ client.connect_callback = mqtt_connect_callback; client.online_callback = mqtt_online_callback; client.offline_callback = mqtt_offline_callback; /* set subscribe table and event callback */ client.messageHandlers[0].topicFilter = rt_strdup(MQTT_SUBTOPIC); client.messageHandlers[0].callback = mqtt_sub_callback; client.messageHandlers[0].qos = MQTT_QOS; /* set default subscribe event callback */ client.defaultMessageHandler = mqtt_sub_callback; } /* run mqtt client */ paho_mqtt_start(&client); return; _exit: if (client.buf) { rt_free(client.buf); client.buf = RT_NULL; } if (client.readbuf) { rt_free(client.readbuf); client.readbuf = RT_NULL; } return; } ``` 对应 **连接**/**订阅**/**上线**/**离线** 回调函数<br> ```c static void mqtt_connect_callback(MQTTClient *c) { LOG_D("mqtt_connect_callback!"); } static void mqtt_sub_callback(MQTTClient *c, MessageData *msg_data) { sub_count++; *((char *)msg_data->message->payload + msg_data->message->payloadlen) = '\0'; rt_kprintf("mqtt sub callback[%u]: \n topic: %.*s \n message %.*s", sub_count, msg_data->topicName->lenstring.len, msg_data->topicName->lenstring.data, msg_data->message->payloadlen, (char *)msg_data->message->payload); } static void mqtt_online_callback(MQTTClient *c) { LOG_D("mqtt_online_callback!"); }