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RT-Thread 连接 EMQ X Cloud with TLS/SSL

本文将使用RT-Thread配合ART-Pi搭建MQTT客户端，快速接入EMQ X Cloud 。

EMQ X Cloud简介

EMQ X Cloud 是由 EMQ 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 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。

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

通过快速入门创建部署EMQX Cloud

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官方IDE RT-Thread-Studio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；

工程配置和引入依赖包

进入配置页面

选择“More”
启用RTC驱动
引入MQTT依赖包
启动TLS需设置mqtt线程栈大小 ≥ 6144
配置mbedtls
1. 若选择用户CA证书(单/双向认证)
2. 若选择无证书SSL连接(单向认证)
保存当前配置，IDE会将配置更新到工程中

修改宏 MEMP_NUM_NETDB 为 2
位于项目路径"rt-thread\components\net\lwip-2.0.2\src\include\lwip\opt.h:488"

/**
 * 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

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

#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);

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；
```
 rt_wlan_connect(WIFI_SSID, WIFI_PASSWORD);
```

分别新建mqtt-client.c和mqtt-client.h;
创建mqtt client

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

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!");
}

static void mqtt_offline_callback(MQTTClient *c)
{
    LOG_D("mqtt_offline_callback!");
}

创建pub线程回调函数和mqtt客户端启动函数

static void thread_pub(void *parameter)
{
    pub_data = rt_malloc(TEST_DATA_SIZE * sizeof(char));
    if (!pub_data)
    {
        rt_kprintf("no memory for pub_data\n");
        return;
    }

    start_tm = time((time_t *) RT_NULL);
    rt_kprintf("test start at '%d'\r\n", start_tm);

    while (1)
    {
        rt_snprintf(pub_data, TEST_DATA_SIZE, "Pub EMQX message-%d", pub_count);

        if (!paho_mqtt_publish(&client, QOS1, MQTT_PUBTOPIC, pub_data))
        {
            ++pub_count;
        }

        rt_thread_delay(PUB_CYCLE_TM);
    }
}

void mqtt_client_start(void)
{
    if (is_started)
    {
        return;
    }

    mqtt_create();

    while (!client.isconnected)
    {
        rt_kprintf("Waiting for mqtt connection...\n");
        rt_thread_delay(1000);
    }

    pub_thread_tid = rt_thread_create("pub_thread", thread_pub, RT_NULL, 1024, 8, 100);
    if (pub_thread_tid != RT_NULL)
    {
        rt_thread_startup(pub_thread_tid);
    }

    is_started = 1;

    return;
}

设置mqtt连接参数和用户名

#define EMQX_Cloud_Professional_Version 1
#define EMQX_Cloud_TLS_SSL 1

#if !EMQX_Cloud_Professional_Version

#if EMQX_Cloud_TLS_SSL
#define MQTT_BROKER_URI         "ssl://ge06f1e1.cn-shenzhen.emqx.cloud:15455"
#else
#define MQTT_BROKER_URI         "tcp://ge06f1e1.cn-shenzhen.emqx.cloud:15915"
#endif
#else

#if EMQX_Cloud_TLS_SSL
#define MQTT_BROKER_URI         "ssl://oba9d641.emqx.cloud:8883"
#else
#define MQTT_BROKER_URI         "tcp://oba9d641.emqx.cloud:1883"
#endif

#endif

#define MQTT_CLIENTID_PREFIX    "rtthread-mqtt"
#define MQTT_USERNAME           "EMQX_RTT"
#define MQTT_PASSWORD           "emqx_rtt_0813"
#define MQTT_SUBTOPIC           "/emqx/mqtt/sub"
#define MQTT_PUBTOPIC           "/emqx/mqtt/pub"
#define MQTT_WILLMSG            "Goodbye!"
#define MQTT_QOS                1