java的mqtt客户端 mqtt客户端编写

RT-Thread开发之路（5）— MQTT通信

基于：使用at_device软件包通过ESP8266连接到网络

一、添加pahomqtt软件包

打开【RT-Thread Settings】，搜索pahomqtt，然后点击添加

然后保存使之生效。

二、编写代码，连接到服务器

首先，包含要用到的头文件：

#include "paho_mqtt.h"

宏定义一些连接mqtt服务器需要的参数：

#define MQTT_Uri    "tcp://39.96.35.207:1883"   // MQTT服务器的地址和端口号
#define ClientId    "BearPi8266"                // ClientId需要唯一
#define UserName    "BearPi"                    // 用户名
#define PassWord    "123456"                    // 用户名对应的密码

接下来定义一个mqtt客户端结构体变量

/* 定义一个MQTT客户端结构体 */
static MQTTClient client;

接下来对MQTT进行配置

/* 对MQTT客户端结构体变量进行配置 */
    client.isconnected = 0;
    client.uri = MQTT_Uri;

    /* 配置MQTT的连接参数 */
    MQTTPacket_connectData condata = MQTTPacket_connectData_initializer;
    memcpy(&client.condata, &condata, sizeof(condata));
    client.condata.clientID.cstring = ClientId;
    client.condata.keepAliveInterval = 30;
    client.condata.cleansession = 1;
    client.condata.username.cstring = (char*)USERNAME;
    client.condata.password.cstring = (char*)PASSWORD;

然后为MQTT的消息缓存申请内存

/* 为mqtt申请内存 */
    client.buf_size = client.readbuf_size = 1024;
    client.buf = rt_calloc(1, client.buf_size);
    client.readbuf = rt_calloc(1, client.readbuf_size);
    if (!(client.buf && client.readbuf))
    {
        rt_kprintf("no memory for MQTT client buffer!\r\n");
        return -1;
    }

接下来我们设置下回调函数，以及订阅一个主题，其中设置的默认的回调函数，是在如果有订阅的 Topic 没有设置回调函数时，则使用该默认回调函数

/* 设置回调函数  */
    client.connect_callback = mqtt_connect_callback;
    client.online_callback = mqtt_online_callback;
    client.offline_callback = mqtt_offline_callback;

    /* 订阅一个主题，并设置其回调函数 */
    client.messageHandlers[0].topicFilter = rt_strdup("BearPi_Sub");
    client.messageHandlers[0].callback = mqtt_sub_callback;
    client.messageHandlers[0].qos = QOS1;

    /* 设置默认的回调函数 */
    client.defaultMessageHandler = mqtt_sub_default_callback;

然后我们实现各个回调函数，并在上线后发布一个主题消息

/* 收到订阅的"Bear_Pi"主题的消息时的回调函数*/
static void mqtt_sub_callback(MQTTClient *c, MessageData *msg_data)
{
    *((char *)msg_data->message->payload + msg_data->message->payloadlen) = '\0';
    rt_kprintf("Receive topic: %.*s, message data:\r\n", msg_data->topicName->lenstring.len, msg_data->topicName->lenstring.data);
    rt_kprintf("%.*s\r\n", msg_data->message->payloadlen, (char *)msg_data->message->payload);
}

/* 默认的订阅回调函数，如果有订阅的 Topic 没有设置回调函数，则使用该默认回调函数 */
static void mqtt_sub_default_callback(MQTTClient *c, MessageData *msg_data)
{
    *((char *)msg_data->message->payload + msg_data->message->payloadlen) = '\0';
    rt_kprintf("Receive topic: %.*s, message data:\r\n", msg_data->topicName->lenstring.len, msg_data->topicName->lenstring.data);
    rt_kprintf("%.*s\r\n", msg_data->message->payloadlen, (char *)msg_data->message->payload);
}

/* 连接成功回调函数 */
static void mqtt_connect_callback(MQTTClient *c)
{
    rt_kprintf("mqtt connect success! \r\n");
}

/* 上线回调函数 */
static void mqtt_online_callback(MQTTClient *c)
{
    rt_kprintf("mqtt online \r\n");
    paho_mqtt_publish(&client, QOS1, "BearPi_Pub", "Hello, I am BearPi with RT_Thread.");
}

都设置好后，就可以启动MQTT连接了

/* 启动 mqtt client */
    paho_mqtt_start(&client);

编译，下载，运行，打开EMQ的控制台，可以看到，已经连接上了

另外我们也可以看到，已经收到了其发布的主题消息

然后我们尝试对其订阅的主题发布一个消息，可以看到，也成功接收到了

三、优化代码

我们修改其程序，将其放入一个线程内，并将该线程的创建放入应用初始化中，并在这个线程中每隔一秒发布一个主题消息。代码如下：

#include <rtthread.h>
#include <board.h>
#include <rtdevice.h>
#include <sys/socket.h>
#include "netdb.h"
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include "paho_mqtt.h"

#define MQTT_Uri    "tcp://39.96.35.207:1883"   // MQTT服务器的地址和端口号
#define ClientId    "BearPi8266"                // ClientId需要唯一
#define UserName    "BearPi"                    // 用户名
#define PassWord    "123456"                    // 用户名对应的密码

/* 定义一个MQTT线程句柄结构体指针 */
static rt_thread_t app_mqtt_thread = RT_NULL;

/* 定义一个MQTT客户端结构体 */
static MQTTClient client;

/* 收到订阅的"Bear_Pi"主题的消息时的回调函数*/
static void mqtt_sub_callback(MQTTClient *c, MessageData *msg_data)
{
    *((char *)msg_data->message->payload + msg_data->message->payloadlen) = '\0';
    rt_kprintf("Receive topic: %.*s, message data:\r\n", msg_data->topicName->lenstring.len, msg_data->topicName->lenstring.data);
    rt_kprintf("%.*s\r\n", msg_data->message->payloadlen, (char *)msg_data->message->payload);
}

/* 默认的订阅回调函数，如果有订阅的 Topic 没有设置回调函数，则使用该默认回调函数 */
static void mqtt_sub_default_callback(MQTTClient *c, MessageData *msg_data)
{
    *((char *)msg_data->message->payload + msg_data->message->payloadlen) = '\0';
    rt_kprintf("Receive topic: %.*s, message data:\r\n", msg_data->topicName->lenstring.len, msg_data->topicName->lenstring.data);
    rt_kprintf("%.*s\r\n", msg_data->message->payloadlen, (char *)msg_data->message->payload);
}

/* 连接成功回调函数 */
static void mqtt_connect_callback(MQTTClient *c)
{
    rt_kprintf("mqtt connect success! \r\n");
}

/* 上线回调函数 */
static void mqtt_online_callback(MQTTClient *c)
{
    rt_kprintf("mqtt online \r\n");
    paho_mqtt_publish(&client, QOS1, "BearPi_Pub", "Hello, I am BearPi with RT_Thread.");
}

/* 下线回调函数 */
static void mqtt_offline_callback(MQTTClient *c)
{
    rt_kprintf("mqtt offline \r\n");
}

static void app_mqtt_thread_entry(void *parameter)
{
    int count = 1;
    char msg_buf[128];
    /* 对MQTT客户端结构体变量进行配置 */
    client.isconnected = 0;
    client.uri = MQTT_Uri;

    /* 配置MQTT的连接参数 */
    MQTTPacket_connectData condata = MQTTPacket_connectData_initializer;
    memcpy(&client.condata, &condata, sizeof(condata));
    client.condata.clientID.cstring = ClientId;
    client.condata.keepAliveInterval = 30;
    client.condata.cleansession = 1;
    client.condata.username.cstring = UserName;
    client.condata.password.cstring = PassWord;

    /* 为mqtt申请内存 */
    client.buf_size = client.readbuf_size = 1024;
    client.buf = rt_calloc(1, client.buf_size);
    client.readbuf = rt_calloc(1, client.readbuf_size);
    if (!(client.buf && client.readbuf))
    {
        rt_kprintf("no memory for MQTT client buffer!\r\n");
        return ;
    }

    /* 设置回调函数  */
    client.connect_callback = mqtt_connect_callback;
    client.online_callback = mqtt_online_callback;
    client.offline_callback = mqtt_offline_callback;

    /* 订阅一个主题，并设置其回调函数 */
    client.messageHandlers[0].topicFilter = rt_strdup("BearPi_Sub");
    client.messageHandlers[0].callback = mqtt_sub_callback;
    client.messageHandlers[0].qos = QOS1;

    /* 设置默认的回调函数 */
    client.defaultMessageHandler = mqtt_sub_default_callback;

    /* 启动 mqtt client */
    paho_mqtt_start(&client);

    while(1)
    {
        rt_sprintf(msg_buf, "publish %d times.", count++);
        paho_mqtt_publish(&client, QOS1, "BearPi_Pub", msg_buf);
        rt_thread_mdelay(1000);
    }
}

static int app_mqtt_init(void)
{
    rt_err_t rt_err;
    /* 创建MQTT线程*/
    app_mqtt_thread = rt_thread_create("app_mqtt thread",
            app_mqtt_thread_entry, RT_NULL, 2048, 6, 10);
    /* 如果获得线程控制块，启动这个线程 */
    if (app_mqtt_thread != RT_NULL)
        rt_err = rt_thread_startup(app_mqtt_thread);
    else
        rt_kprintf("app_mqtt_thread create failure !!! \n");

    /* 判断线程是否启动成功 */
    if( rt_err == RT_EOK)
        rt_kprintf("app_mqtt_thread startup ok. \n");
    else
        rt_kprintf("app_mqtt_thread startup err. \n");

    return rt_err;
}

INIT_APP_EXPORT(app_mqtt_init);

运行后可以收到主题消息: