OpenHarmony轻量系统开发【11】移植MQTT

摘要：本文简单介绍如何移植MQTT
适合群体：适用于润和Hi3861开发板
文中所有代码仓库：https://gitee.com/qidiyun/hihope-3861-smart-home-kit

11.1 MQTT介绍

MQTT 是当前最主流的物联网通信协议，需要物联网云平台，例如华为云、阿里云、移动OneNET都支持mqtt。而Hi3861则是一款专为IoT应用场景打造的芯片。本节主要讲如何在鸿蒙系统中通过移植第3方软件包 paho mqtt去实现MQTT协议功能，最后会给出测试验证。为后续的物联网项目打好基础。

友情预告，本节内容较多，源码也贴出来了，大家最好先看一遍，然后再操作一次。

已经移植好的MQTT源码：
https://gitee.com/qidiyun/harmony_mqtt

11.2 MQTT移植

如果不想要自己移植的，可以跳过本节
MQTT 全称为 Message Queuing Telemetry Transport（消息队列遥测传输）是一种基于发布/订阅范式的二进制“轻量级”消息协议，由IB公司发布。针对于网络受限和嵌入式设备而设计的一种数据传输协议。MQTT最大优点在于，可以以极少的代码和有限的带宽，为连接远程设备提供实时可靠的消息服务。作为一种低开销、低带宽占用的即时通讯协议，使其在物联网、小型设备、移动应用等方面有较广泛的应用。MQTT模型如图所示。

更多MQTT协议的介绍见这篇文章： MQTT 协议开发入门

1. 下载paho mqtt软件包，添加到鸿蒙代码中

paho mqtt-c 是基于C语言实现的MQTT客户端，非常适合用在嵌入式设备上。首先下载源码：

https://github.com/eclipse/paho.mqtt.embedded-c

下载之后解压，会得到这么一个文件夹：

如何在鸿蒙系统中移植 Paho-MQTT 实现MQTT协议-鸿蒙HarmonyOS技术社区

我们在鸿蒙系统源码的 third_party 文件夹下创建一个 pahomqtt 文件夹，然后把解压后的所有文件都拷贝到 pahomqtt 文件夹下

下一步，我们在pahomqtt 文件夹下面新建BUILD.gn文件，用来构建编译。其内容如下：

# 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("//build/lite/config/component/lite_component.gni")
import("//build/lite/ndk/ndk.gni")config("pahomqtt_config") {include_dirs = ["MQTTPacket/src","MQTTClient-C/src","MQTTClient-C/src/liteOS","//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_sourcespublic_configs = [ ":pahomqtt_config" ]
}lite_library("pahomqtt_shared") {target_type = "shared_library"sources = pahomqtt_sourcespublic_configs = [ ":pahomqtt_config" ]
}ndk_lib("pahomqtt_ndk") {if (board_name != "hi3861v100") {lib_extension = ".so"deps = [":pahomqtt_shared"]} else {deps = [":pahomqtt_static"]}head_files = ["//third_party/pahomqtt"]
}

2. 移植

我们使用到的是MQTTClient-C的代码，该代码支持多线程。

（1）创建LiteOS文件夹
MQTT已经提供了Linux和freertos的移植，这里我们参考，新建文件夹：
third_party\pahomqtt\MQTTClient-C\src\liteOS
里面存放两个文件：
MQTTLiteOS.c 和 MQTTLiteOS.h

内容如下：

#include "MQTTLiteOS.h"//用来创建线程
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;
}
//定时器初始化
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\n", (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);
}//接受数据
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;}elsebytes += rc;}return bytes;
}//写数据
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 errorssetsockopt(n->my_socket, SOL_SOCKET, SO_SNDTIMEO, (char *)&tv,sizeof(struct timeval));int  rc = send(n->my_socket, buffer, len, 0);return rc;
}//网络初始化
void NetworkInit(Network* n)
{n->my_socket = 0;n->mqttread = ohos_read;n->mqttwrite = ohos_write;
}//网络连接
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;}elserc = -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));elserc = -1;}return rc;
}void NetworkDisconnect(Network* n)
{close(n->my_socket);
}

至此我们移植基本结束

11.3 测试代码

测试代码比较好写。主要是3个文件，内容我都贴出来了：

（1）BUILD.gn文件内容：

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

（2）mqtt_entry.c文件
主要是进行热点连接，因为我们要使用MQTT需要用到网络。热点连接的代码之前在第9章已经讲说，这里就不完全贴了，代码仓库也有，主要的代码部分：

void wifi_sta_task(void *arg)
{arg = arg;//连接热点hi_wifi_start_sta();while(wifi_ok_flg == 0){usleep(30000);}usleep(2000000);//开始进入MQTT测试mqtt_test();
}

（3）mqtt_test.c 文件则是编写了一个简单的MQTT测试代码

其中测试用的mqtt服务器是我自己的服务器：5.196.95.208
大家也可以改成自己的。

#include <stdio.h>
#include <unistd.h>
#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;  //消息回调函数
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\r\n", msg_data->topicName->lenstring.len, msg_data->topicName->lenstring.data);printf("message is %.*s\r\n", 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;//连接服务器rc = MQTTConnect(&mq_client, &data);//订阅消息，并设置回调函数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");//发送消息if (MQTTPublish(&mq_client, "ohospub", &message) < 0){return -1;}}return 0;
}void mqtt_test(void)
{mqtt_connect();
}

到这里就完成了代码部分，可以开始编译了。

11.4 实验

这里我们需要先下载一个 Windows电脑端的 MQTT客户端，这样我们就可以用电脑订阅开发板的MQTT主题信息了。

电脑版的mqtt客户端下载链接： https://repo.eclipse.org/content/repositories/paho-releases/org/eclipse/paho/org.eclipse.paho.ui.app/1.1.1/

我们选择这一个：

弄完后打开软件，按图操作：

此时我们去查看我们电脑端的MQTT客户端软件，可以看到右边已经有接收MQTT信息了，主题未 ohospub，消息内容为 openharmony，说明实验成功。

电脑发送主题为ohossub，内容为123456，查看串口打印，可以看到也收到了数据