1、参考链接 ：

2、首先移植好lwip,然后添加\src\apps\mqtt  文件下 的 mqtt.c 文件，如果有头文件问题，清解决头文件问题！

3、根据参考链接，做一下修改

下面代码中的MQTT 服务器 是我自己搭建的，你也可以找一台Linux 主机搭建一个。。2017年4月24日09:10:19

/* * MQTT client for lwIP * Author: Erik Andersson * Details of the MQTT protocol can be found at:     http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html  * */#include "oneNet_MQTT.h"#include "string.h"ip_addr_t mqttServerIpAddr;//1. Initial steps, reserve memory and make connection to server://1.1: Provide storage//Static allocation: //下面这两句转移到 MAIN.c 中//  mqtt_client_t static_client;//  example_do_connect(&static_client);//Dynamic allocation://  mqtt_client_t *client = mqtt_client_new();//  if(client != NULL) {//    example_do_connect(&client);//  }//1.2: Establish Connection with servervoid example_do_connect(mqtt_client_t *client){  struct mqtt_connect_client_info_t ci;      err_t err;    /* Setup an empty client info structure */  memset(&ci, 0, sizeof(ci));    /* Minimal amount of information required is client identifier, so set it here */   ci.client_id = "lwip_test";        // MQTT服务器地址为：59.110.142.105端口号为：1883    IP4_ADDR(&mqttServerIpAddr, 59, 110, 142, 105);//配置 MQTT 服务器地址    /* Initiate client and connect to server, if this fails immediately an error code is returned     otherwise mqtt_connection_cb will be called with connection result after attempting      to establish a connection with the server.      For now MQTT version 3.1.1 is always used */      //MQTT 服务器进行连接 ,并注册 “连接结果处理”的回调函数，2017年4月12日09:00:12      err = mqtt_client_connect(client, &mqttServerIpAddr, 1883, mqtt_connection_cb, 0, &ci);    /* For now just print the result code if something goes wrong */  if(err != ERR_OK)     {    printf("mqtt_connect return %d\n", err);  }}//Connection to server can also be probed by calling mqtt_client_is_connected(client) //-----------------------------------------------------------------//2. Implementing the connection status callback//执行连接状态 的 回调函数static void mqtt_connection_cb(mqtt_client_t *client, void *arg, mqtt_connection_status_t status){  err_t err;  if(status == MQTT_CONNECT_ACCEPTED)     {    printf("mqtt_connection_cb: Successfully connected\n");        /* Setup callback for incoming publish requests */        //注册 消息推送 回调函数 以及消息数据到来的处理函数    mqtt_set_inpub_callback(client, mqtt_incoming_publish_cb, mqtt_incoming_data_cb, arg);        /* Subscribe to a topic named "subtopic" with QoS level 2, call mqtt_sub_request_cb with result */     err = mqtt_subscribe(client, "subtopic", 2, mqtt_sub_request_cb, arg);    if(err != ERR_OK)        {      printf("mqtt_subscribe return: %d\n", err);    }  }     else     {    printf("mqtt_connection_cb: Disconnected, reason: %d\n", status);        /* Its more nice to be connected, so try to reconnect */    example_do_connect(client);  }  }void mqtt_sub_request_cb(void *arg, err_t result){  /* Just print the result code here for simplicity,      normal behaviour would be to take some action if subscribe fails like      notifying user, retry subscribe or disconnect from server */  printf("Subscribe result: %d\n", result);}//-----------------------------------------------------------------//3. Implementing callbacks for incoming publish and data/* The idea is to demultiplex topic and create some reference to be used in data callbacks   Example here uses a global variable, better would be to use a member in arg   If RAM and CPU budget allows it, the easiest implementation might be to just take a copy of   the topic string and use it in mqtt_incoming_data_cb*///这两个函数 一个 处理 消息头 一个 处理 具体的 数据static int inpub_id;static void mqtt_incoming_publish_cb(void *arg, const char *topic, u32_t tot_len){        //消息来了之后，先进入这里用于判断 是什么主题 的，2017年4月20日09:25:51      printf("Incoming publish at topic \" %s \" with total length %u\r\n", topic, (unsigned int)tot_len);  /* Decode topic string into a user defined reference */  if(strcmp(topic, "subtopic") == 0)     {    inpub_id = 0;  }     else if(topic[0] == 'A')            {    /* All topics starting with 'A' might be handled at the same way */    inpub_id = 1;  }    else    {    /* For all other topics */    inpub_id = 2;  }}static void mqtt_incoming_data_cb(void *arg, const u8_t *data, u16_t len, u8_t flags){    //消息来了之后先判断主题 上面那个函数，然后在这里是根据不同的主题，进行不同的处理        uint8_t tempBuff[20]={
   0};        uint8_t i;        //数据复制到到缓冲区，并加  字符‘0’结尾，因为 发送工具只能发送 字符 不能发送字符串，2017年4月20日09:24:43    for(i=0;i
     
      =1        *    只有一次，确保消息只有一次到达。即：＝1。在一些要求比较严格的计费系统中，可以使用此级别      */  u8_t qos = 2; /* 0 1 or 2, see MQTT specification */        //=0 的意思应该是不保留有效负载（有效数据）  u8_t retain = 0; /* No don't retain such crappy payload... */      err = mqtt_publish(client, "pub_topic", pub_payload, strlen(pub_payload), qos, retain, mqtt_pub_request_cb, arg);      if(err != ERR_OK)    {    printf("Publish err: %d.\r\n", err);  }    else    {      printf("Publish Success.\r\n");    }}/* Called when publish is complete either with sucess or failure *///推送消息完成后 的 回调函数void mqtt_pub_request_cb(void *arg, err_t result){  if(result != ERR_OK)    {    printf("Publish result: %d\n", result);  }}//-----------------------------------------------------------------//5. Disconnecting//Simply call mqtt_disconnect(client)
     

static_client.conn_state=0;        /* Initialize MQTT client */  example_do_connect(&static_client);        while(1)    {                    example_publish(&static_client,(void *)mqtt_pub_request_cb);                    /* vTaskDelayUntil是绝对延迟，vTaskDelay是相对延迟。*/        vTaskDelay(2000);    }

 上面 的服务器 地址 今天 已经 到期了 ，阿里 的 太贵了 没钱 续费了  哎 2017年6月26日17:15:40