1、参考链接 ：/lwip/2_0_x/group__mqtt.html
2、首先移植好lwip,然后添加lwip-2.0.2\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。。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-/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：1883IP4_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 returnedotherwise 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，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 callbacksExample here uses a global variable, better would be to use a member in argIf RAM and CPU budget allows it, the easiest implementation might be to just take a copy ofthe 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，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，4月20日09:24:43for(i=0;i<len;i++){tempBuff[i]=data[i];}tempBuff[i]=0;printf("Incoming publish payload with length %d, flags %u\n", len, (unsigned int)flags);if(flags & MQTT_DATA_FLAG_LAST) {/* Last fragment of payload received (or whole part if payload fits receive bufferSee MQTT_VAR_HEADER_BUFFER_LEN) *//* Call function or do action depending on reference, in this case inpub_id */if(inpub_id == 0) {/* Don't trust the publisher, check zero termination */if(tempBuff[len] == 0) {printf("mqtt_incoming_data_cb: %s\n", (const char *)data);}}else if(inpub_id == 1) {/* Call an 'A' function... */}else {printf("mqtt_incoming_data_cb: Ignoring payload...\n");}}else {/* Handle fragmented payload, store in buffer, write to file or whatever */}}//-----------------------------------------------------------------//4. Using outgoing publish//使用 向外推送消息//MQTT传输的消息分为：主题（Topic）和负载（payload）两部分void example_publish(mqtt_client_t *client, void *arg){const char *pub_payload= "Hello,MQTT!\r\n";//推送的有效数据(负载) err_t err;/** 最多一次，这一级别会发生消息丢失或重复，消息发布依赖于底层TCP/IP网络。即：<=1* 至多一次，这一级别会确保消息到达，但消息可能会重复。即：>=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 6月26日17:15:40
