MQTT协议在STM32上的移植

MQTT协议在STM32上的移植

The Eclipse Paho project provides open-source client implementations of MQTT and MQTT-SN messaging protocols aimed at new, existing, and emerging applications for the Internet of Things (IoT).

开发平台

软件环境

• Keil uVision 5.12
• STM32F10x_StdPeriph_Lib_V3.5.0 标准库

硬件环境

• stm32f103系列
• SIM800C无线通讯GSM模块

参考文档

• MQTT协议中文版

下载MQTT 嵌入式C/C++库

本篇是MQTT在STM32设备上的移植，因此使用paho的嵌入式C库,源码地址https://github.com/eclipse/paho.mqtt.embedded-c.

移植

首先，需要将../paho.mqtt.embedded-c/MQTTPacket/中的所有文件添加到keil工程文件，然后参考../paho.mqtt.embedded-c/MQTTPacket/samples/中的例程编写。

移植的前提是保证已经建立TCP连接，因为MQTT协议实在TCP基础上的数据传输协议。本实验使用sim800c无线通讯模块先与MQTT服务器建立TCP连接（使用透传模式），再通过串口与stm32建立通讯联系。

接口函数

移植主要参考修改库中的../paho.mqtt.embedded-c/MQTTPacket/samples/transport.c例程文件
，且主要是transport_sendPacketBuffer()和transport_getdata()函数，分别用来作为硬件实现发送和接收数据包的接口函数，因此需要针对硬件平台做相应修改。

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int32_t transport_sendPacketBuffer(uint8_t* buf, uint32_t buflen) {     int rc = 0;         SendBuffer(UART4, buf, buflen);         return rc; } int32_t transport_getdata(uint8_t* buf, int32_t count) {     int32_t n, rc = 0;         memcpy(buf, (void*)&RxBuffer4[readBufLen], count);     readBufLen += count;         return count; }

连接

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uint8_t mqtt_connect(void) {     MQTTPacket_connectData data = MQTTPacket_connectData_initializer;     int rc = 0;     uint8_t buf[200];     int buflen = sizeof(buf);     int mysock = 0;     MQTTString topicString = MQTTString_initializer;     int len = 0;     data.clientID.cstring = "yao";     data.keepAliveInterval = 20;      //seconds     data.cleansession = 1;     data.username.cstring = "nncy";     data.password.cstring = "nncy";     data.MQTTVersion = 4;     len = MQTTSerialize_connect((unsigned char *)buf, buflen, &data); //    len += MQTTSerialize_disconnect((unsigned char *)(buf + len), buflen - len);     rc = transport_sendPacketBuffer(buf, len);     printf("len:%d|rc:%d\r\n", len, rc);         reset_receive_buf();         /* wait for connack */     if (MQTTPacket_read(buf, buflen, transport_getdata) == CONNACK)     {         unsigned char sessionPresent, connack_rc;         if (MQTTDeserialize_connack(&sessionPresent, &connack_rc, buf, buflen) != 1 || connack_rc != 0)         {             printf("Unable to connect, return code %d\n", connack_rc);             return 0;         }         else         {             printf("MQTT CONNECT!\n");         }     }     else         printf("no connack\n");         return 0; }

订阅和发布函数

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void mqtt_publish(char *pPubTopic, char *pMessage) {     MQTTPacket_connectData data = MQTTPacket_connectData_initializer;     int rc = 0;     uint8_t buf[200];     int buflen = sizeof(buf);     int mysock = 0;     MQTTString topicString = MQTTString_initializer;     char* payload = pMessage;     int payloadlen = strlen(payload);     int len = 0;     topicString.cstring = pPubTopic;     len += MQTTSerialize_publish((unsigned char *)(buf + len), buflen - len, 0, 0, 0, 0, topicString, (unsigned char *)payload, payloadlen); //    len += MQTTSerialize_disconnect((unsigned char *)(buf + len), buflen - len);     rc = transport_sendPacketBuffer(buf, len) } uint8_t mqtt_subscribe(char *pSubTopic) {     uint8_t buf[200] = {0};     uint32_t buflen = sizeof(buf);     int32_t msgid = 1;     int32_t req_qos = 0;     uint32_t rc, len = 0;     MQTTString topicString = MQTTString_initializer;     topicString.cstring = pSubTopic;         len = MQTTSerialize_subscribe(buf, buflen, 0, msgid, 1, &topicString, &req_qos);     rc = transport_sendPacketBuffer(buf, len);     reset_receive_buf();     if (MQTTPacket_read(buf, buflen, transport_getdata) == SUBACK) /* wait for suback */     {         unsigned short submsgid;         int subcount;         int granted_qos;         rc = MQTTDeserialize_suback(&submsgid, 1, &subcount, &granted_qos, buf, buflen);         if (granted_qos != 0)         {             printf("granted qos != 0, %d\n", granted_qos);             return 0;         }         else         {             printf("granted qos = 0\n");             return 1;         }     }     else         printf("no suback received!\r\n");         return 0; }

接收数据包解析函数

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bool MQTT_Received_Data_Parser(char *Topic, char *message) {     uint8_t len = 0;     uint8_t buf[256];         len = uart4RxBufLen;     printf("Received data lenth:%d\r\n", len);         if (strstr(RxBuffer4, "CLOSED")){         GPRS_CIP_MODE = 0;         return false;     } else {         memcpy(buf, (void*)&RxBuffer4, len);             printf("buf:%s\r\n", buf);         printf("topicLength:%d\r\n", buf[3]);         printf("Topic: %s\r\n", buf+4);         printf("dataLength:%d\r\n", buf[1]-buf[3]-2);         printf("Message: %s\r\n", buf+4+buf[3]);                         if (0xD0 == *buf) {             printf("MQTT Heart Beat \r\n");         } else {             strncpy(Topic,(void*)(buf+4),buf[3]);             printf("Topic: %s\r\n", Topic);             strncpy(message,(void*)(buf+4+buf[3]),buf[1]-buf[3]-2);             printf("Message: %s\r\n", message);                         memset(buf,0,sizeof(buf));         }     }     return true; }

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