摘要

本文簡單介紹如何移植MQTT

適合群體

適用于潤和Hi3861開發(fā)板的開發(fā)人員。

1、MQTT介紹

MQTT 是當前最主流的物聯(lián)網通信協(xié)議，需要物聯(lián)網云平臺，例如華為云、阿里云、移動OneNET都支持mqtt。而Hi3861則是一款專為IoT應用場景打造的芯片。本節(jié)主要講如何在鴻蒙系統(tǒng)中通過移植第3方軟件包 paho mqtt去實現(xiàn)MQTT協(xié)議功能，最后會給出測試驗證。為后續(xù)的物聯(lián)網項目打好基礎。

友情預告，本節(jié)內容較多，源碼也貼出來了，大家最好先看一遍，然后再操作一次。

已經移植好的MQTT源碼：

2、MQTT移植

如果不想要自己移植的，可以跳過本節(jié)。MQTT 全稱為 Message Queuing Telemetry Transport（消息隊列遙測傳輸）是一種基于發(fā)布/訂閱范式的二進制“輕量級”消息協(xié)議，由IB公司發(fā)布。針對于網絡受限和嵌入式設備而設計的一種數(shù)據(jù)傳輸協(xié)議。MQTT最大優(yōu)點在于，可以以極少的代碼和有限的帶寬，為連接遠程設備提供實時可靠的消息服務。作為一種低開銷、低帶寬占用的即時通訊協(xié)議，使其在物聯(lián)網、小型設備、移動應用等方面有較廣泛的應用。MQTT模型如圖所示。

更多MQTT協(xié)議的介紹見這篇文章：MQTT 協(xié)議開發(fā)入門

1）下載paho mqtt軟件包，添加到鴻蒙代碼中

paho mqtt-c 是基于C語言實現(xiàn)的MQTT客戶端，非常適合用在嵌入式設備上。首先下載源碼：

下載之后解壓，會得到這么一個文件夾：

如何在鴻蒙系統(tǒng)中移植 Paho-MQTT 實現(xiàn)MQTT協(xié)議-鴻蒙HarmonyOS技術社區(qū)

我們在鴻蒙系統(tǒng)源碼的 third_party 文件夾下創(chuàng)建一個 pahomqtt 文件夾，然后把解壓后的所有文件都拷貝到 pahomqtt 文件夾下。

下一步，我們在pahomqtt 文件夾下面新建BUILD.gn文件，用來構建編譯。其內容如下：

# Copyright (c) 2020 Huawei Device Co., Ltd.# Licensed under the Apache License, Version 2.0 (the "License");# you may not use this file except in compliance with the License.# You may obtain a copy of the License at##   http://www.apache.org/licenses/LICENSE-2.0## Unless required by applicable law or agreed to in writing, software# distributed under the License is distributed on an "AS IS" BASIS,# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.# See the License for the specific language governing permissions and# limitations under the License.
import("http://build/lite/config/component/lite_component.gni")import("http://build/lite/ndk/ndk.gni")
config("pahomqtt_config") {  include_dirs = [    "MQTTPacket/src",    "MQTTClient-C/src",    "MQTTClient-C/src/liteOS",    "http://kernel/liteos_m/components/cmsis/2.0",  ]}
pahomqtt_sources = ["MQTTClient-C/src/liteOS/MQTTLiteOS.c","MQTTClient-C/src/MQTTClient.c",
"MQTTPacket/src/MQTTConnectClient.c","MQTTPacket/src/MQTTConnectServer.c","MQTTPacket/src/MQTTDeserializePublish.c","MQTTPacket/src/MQTTFormat.c","MQTTPacket/src/MQTTPacket.c","MQTTPacket/src/MQTTSerializePublish.c","MQTTPacket/src/MQTTSubscribeClient.c","MQTTPacket/src/MQTTSubscribeServer.c","MQTTPacket/src/MQTTUnsubscribeClient.c","MQTTPacket/src/MQTTUnsubscribeServer.c",]
lite_library("pahomqtt_static") {  target_type = "static_library"  sources = pahomqtt_sources  public_configs = [ ":pahomqtt_config" ]}
lite_library("pahomqtt_shared") {  target_type = "shared_library"  sources = pahomqtt_sources  public_configs = [ ":pahomqtt_config" ]}
ndk_lib("pahomqtt_ndk") {  if (board_name != "hi3861v100") {    lib_extension = ".so"    deps = [      ":pahomqtt_shared"    ]  } else {    deps = [      ":pahomqtt_static"    ]  }  head_files = [    "http://third_party/pahomqtt"  ]}

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2）移植

我們使用到的是MQTTClient-C的代碼，該代碼支持多線程。

（1）創(chuàng)建LiteOS文件夾

MQTT已經提供了Linux和freertos的移植，這里我們參考，新建文件夾：third_partypahomqttMQTTClient-CsrcliteOS，里面存放兩個文件：MQTTLiteOS.c 和 MQTTLiteOS.h，內容如下：

#include "MQTTLiteOS.h"
//用來創(chuàng)建線程int ThreadStart(Thread* thread, void (*fn)(void*), void* arg){ int rc = 0; thread = thread;
 osThreadAttr_t attr;
  attr.name = "MQTTTask";  attr.attr_bits = 0U;  attr.cb_mem = NULL;  attr.cb_size = 0U;  attr.stack_mem = NULL;  attr.stack_size = 2048;  attr.priority = osThreadGetPriority(osThreadGetId());
  rc = (int)osThreadNew((osThreadFunc_t)fn, arg, &attr);
 return rc;}//定時器初始化void TimerInit(Timer* timer){ timer->end_time = (struct timeval){0, 0};}
char TimerIsExpired(Timer* timer){ struct timeval now, res; gettimeofday(&now, NULL); timersub(&timer->end_time, &now, &res); return res.tv_sec < 0 || (res.tv_sec == 0 && res.tv_usec <= 0);}

void TimerCountdownMS(Timer* timer, unsigned int timeout){ struct timeval now; gettimeofday(&now, NULL); struct timeval interval = {timeout / 1000, (timeout % 1000) * 1000}; timeradd(&now, &interval, &timer->end_time);}

void TimerCountdown(Timer* timer, unsigned int timeout){ struct timeval now; gettimeofday(&now, NULL); struct timeval interval = {timeout, 0}; timeradd(&now, &interval, &timer->end_time);}

int TimerLeftMS(Timer* timer){ struct timeval now, res; gettimeofday(&now, NULL); timersub(&timer->end_time, &now, &res); //printf("left %d ms
", (res.tv_sec < 0) ? 0 : res.tv_sec * 1000 + res.tv_usec / 1000); return (res.tv_sec < 0) ? 0 : res.tv_sec * 1000 + res.tv_usec / 1000;}
void MutexInit(Mutex* mutex){ mutex->sem = osSemaphoreNew(1, 1, NULL);}
int MutexLock(Mutex* mutex){ return osSemaphoreAcquire(mutex->sem, LOS_WAIT_FOREVER);}
int MutexUnlock(Mutex* mutex){ return osSemaphoreRelease(mutex->sem);}
//接受數(shù)據(jù)int ohos_read(Network* n, unsigned char* buffer, int len, int timeout_ms){ struct timeval interval = {timeout_ms / 1000, (timeout_ms % 1000) * 1000}; if (interval.tv_sec < 0 || (interval.tv_sec == 0 && interval.tv_usec <= 0)) {  interval.tv_sec = 0;  interval.tv_usec = 100; }
 setsockopt(n->my_socket, SOL_SOCKET, SO_RCVTIMEO, (char *)&interval, sizeof(struct timeval));
 int bytes = 0; while (bytes < len) {  int rc = recv(n->my_socket, &buffer[bytes], (size_t)(len - bytes), 0);  if (rc == -1)  {   if (errno != EAGAIN && errno != EWOULDBLOCK)    bytes = -1;   break;  }  else if (rc == 0)  {   bytes = 0;   break;  }  else   bytes += rc; } return bytes;}
//寫數(shù)據(jù)int ohos_write(Network* n, unsigned char* buffer, int len, int timeout_ms){ struct timeval tv;
 tv.tv_sec = 0; /* 30 Secs Timeout */ tv.tv_usec = timeout_ms * 1000; // Not init'ing this can cause strange errors
 setsockopt(n->my_socket, SOL_SOCKET, SO_SNDTIMEO, (char *)&tv,sizeof(struct timeval)); int rc = send(n->my_socket, buffer, len, 0); return rc;}
//網絡初始化void NetworkInit(Network* n){ n->my_socket = 0; n->mqttread = ohos_read; n->mqttwrite = ohos_write;}
//網絡連接int NetworkConnect(Network* n, char* addr, int port){ int type = SOCK_STREAM; struct sockaddr_in address; int rc = -1; sa_family_t family = AF_INET; struct addrinfo *result = NULL; struct addrinfo hints = {0, AF_UNSPEC, SOCK_STREAM, IPPROTO_TCP, 0, NULL, NULL, NULL};
 if ((rc = getaddrinfo(addr, NULL, &hints, &result)) == 0) {  struct addrinfo* res = result;
  /* prefer ip4 addresses */  while (res)  {   if (res->ai_family == AF_INET)   {    result = res;    break;   }   res = res->ai_next;  }
  if (result->ai_family == AF_INET)  {   address.sin_port = htons(port);   address.sin_family = family = AF_INET;   address.sin_addr = ((struct sockaddr_in*)(result->ai_addr))->sin_addr;  }  else   rc = -1;
  freeaddrinfo(result); }
 if (rc == 0) {  n->my_socket = socket(family, type, 0);  if (n->my_socket != -1)   rc = connect(n->my_socket, (struct sockaddr*)&address, sizeof(address));  else   rc = -1; }
 return rc;}

void NetworkDisconnect(Network* n){ close(n->my_socket);}

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至此我們移植基本結束。

3、代碼測試

測試代碼比較好寫。主要是3個文件，內容我都貼出來了：

（1）BUILD.gn文件內容：

static_library("mqtt_test") {  sources = [    "mqtt_test.c",    "mqtt_entry.c"  ]
  include_dirs = [    "http://utils/native/lite/include",    "http://kernel/liteos_m/components/cmsis/2.0",    "http://base/iot_hardware/interfaces/kits/wifiiot_lite",    "http://vendor/hisi/hi3861/hi3861/third_party/lwip_sack/include",    "http://foundation/communication/interfaces/kits/wifi_lite/wifiservice",    "http://third_party/pahomqtt/MQTTPacket/src",    "http://third_party/pahomqtt/MQTTClient-C/src",    "http://third_party/pahomqtt/MQTTClient-C/src/liteOS",  ]#表示需要a_myparty 軟件包  deps = [    "http://third_party/pahomqtt:pahomqtt_static",  ]}

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（2）mqtt_entry.c文件

主要是進行熱點連接，因為我們要使用MQTT需要用到網絡。熱點連接的代碼之前在第9章已經講說，這里就不完全貼了，代碼倉庫也有，主要的代碼部分：

void wifi_sta_task(void *arg){  arg = arg;    //連接熱點  hi_wifi_start_sta();
  while(wifi_ok_flg == 0)  {    usleep(30000);  }      usleep(2000000);
  //開始進入MQTT測試  mqtt_test();}

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（3）mqtt_test.c 文件則是編寫了一個簡單的MQTT測試代碼

其中測試用的mqtt服務器是我自己的服務器：5.196.95.208，大家也可以改成自己的。

#include #include #include "ohos_init.h"#include "cmsis_os2.h"
#include "hi_wifi_api.h"#include "lwip/ip_addr.h"#include "lwip/netifapi.h"#include "lwip/sockets.h"
#include "MQTTClient.h"

static MQTTClient mq_client;
 unsigned char *onenet_mqtt_buf; unsigned char *onenet_mqtt_readbuf; int buf_size;
Network n;MQTTPacket_connectData data = MQTTPacket_connectData_initializer; 
//消息回調函數(shù)void mqtt_callback(MessageData *msg_data){  size_t res_len = 0;  uint8_t *response_buf = NULL;  char topicname[45] = { "$crsp/" };
  LOS_ASSERT(msg_data);
  printf("topic %.*s receive a message
", msg_data->topicName->lenstring.len, msg_data->topicName->lenstring.data);
  printf("message is %.*s
", msg_data->message->payloadlen, msg_data->message->payload);
}
int mqtt_connect(void){ int rc = 0;   NetworkInit(&n); NetworkConnect(&n, "5.196.95.208", 1883);
  buf_size = 2048;  onenet_mqtt_buf = (unsigned char *) malloc(buf_size);  onenet_mqtt_readbuf = (unsigned char *) malloc(buf_size);  if (!(onenet_mqtt_buf && onenet_mqtt_readbuf))  {    printf("No memory for MQTT client buffer!");    return -2;  }
 MQTTClientInit(&mq_client, &n, 1000, onenet_mqtt_buf, buf_size, onenet_mqtt_readbuf, buf_size);   MQTTStartTask(&mq_client);

  data.keepAliveInterval = 30;  data.cleansession = 1; data.clientID.cstring = "ohos_hi3861"; data.username.cstring = "123456"; data.password.cstring = "222222";
 data.keepAliveInterval = 10; data.cleansession = 1;   mq_client.defaultMessageHandler = mqtt_callback;
 //連接服務器 rc = MQTTConnect(&mq_client, &data);
 //訂閱消息，并設置回調函數(shù) MQTTSubscribe(&mq_client, "ohossub", 0, mqtt_callback);
 while(1) {  MQTTMessage message;
  message.qos = QOS1;  message.retained = 0;  message.payload = (void *)"openharmony";  message.payloadlen = strlen("openharmony");
  //發(fā)送消息  if (MQTTPublish(&mq_client, "ohospub", &message) < 0)  {   return -1;  } }
 return 0;}

void mqtt_test(void){  mqtt_connect();}

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到這里就完成了代碼部分，可以開始編譯了。

4、編譯

這里我們需要先下載一個 Windows電腦端的 MQTT客戶端，這樣我們就可以用電腦訂閱開發(fā)板的MQTT主題信息了。

我們選擇這一個：

弄完后打開軟件，按圖操作：

此時我們去查看 我們電腦端的MQTT客戶端軟件，可以看到右邊已經有接收MQTT信息了，主題未 ohospub，消息內容為 openharmony，說明實驗成功。

電腦發(fā)送主題為ohossub，內容為123456，查看串口打印，可以看到也收到了數(shù)據(jù)。

本節(jié)移植MQTT的教程就到這里了，下一篇我們給大家分享：OneNET云接入，歡迎大家持續(xù)關注哦~

原文標題：OpenHarmony輕量系統(tǒng)開發(fā)【11】移植MQTT