HI3861学习笔记（24）——MQTT客户端

一、MQTT简介

1.1 实现方式

实现MQTT协议需要客户端和服务器端通讯完成，在通讯过程中，MQTT协议中有三种身份：发布者（Publish）、代理（Broker）（服务器）、订阅者（Subscribe）。其中，消息的发布者和订阅者都是客户端，消息代理是服务器，消息发布者可以同时是订阅者。

MQTT传输的消息分为：主题（Topic）和负载（payload）两部分：

Topic，可以理解为消息的类型，订阅者订阅（Subscribe）后，就会收到该主题的消息内容（payload）；

payload，可以理解为消息的内容，是指订阅者具体要使用的内容。

• MQTT服务器的主要工作是数据分发，没有数据保存功能。
• 可以订阅自己发布的主题，服务器就是回发测试。
• MQTT让逻辑变得更清晰，需要什么订阅什么。
• 走标准化流程，解放了私有协议制定、实现、调试、测试一整套复杂的流程。

1.2 Paho MQTT

Eclipse Paho项目是IBM在2011年建立的Eclipse开源项目，该项目包含以C、Java、Python、Javascript等语言编写的可用客户端。

二、移植Paho MQTT

2.1 下载源码

嵌入式C语言客户端开源地址：https://github.com/eclipse/paho.mqtt.embedded-c

下载之后解压，会得到这么一个文件夹：

• MQTTClient： 封装MQTTPacket生成的高级别C++客户端程序。
• MQTTClient-C： 封装MQTTPacket生成的高级别C客户端程序
  • samples目录提供FreeRTOS和Linux两个例程，分别支持FreeRTOS和Linux系统。
  • src目录提供MQTTClient的代码实现能力，以及用于移植到对应平台的网络驱动。
• MQTTPacket： 提供MQTT数据包的序列化与反序列化，以及部分辅助函数。
  

2.2 新建BUILD.gn

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

下一步，我们在 paho_mqtt 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",
        "//third_party/iot_link/network/mqtt/mqtt_al",
        "//third_party/iot_link/inc",
        "//vendor/hisi/hi3861/hi3861/third_party/lwip_sack/include",
        "//kernel/liteos_m/components/cmsis/2.0",
    ]
}
    cflags = [ "-Wno-unused-variable" ]
    cflags += [ "-Wno-unused-but-set-variable" ]
    cflags += [ "-Wno-unused-parameter" ]
    cflags += [ "-Wno-sign-compare" ]
    cflags += [ "-Wno-unused-function" ]
    cflags += [ "-Wno-return-type" ]
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",
"MQTTPacket/samples/transport.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 = [
        "//third_party/paho_mqtt"
    ]
}

2.3 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\paho_mqtt\MQTTClient-C\src\liteOS 里面存放两个文件：
MQTTLiteOS.c 和 MQTTLiteOS.h

内容如下：

2.3.1 MQTTLiteOS.c

/*******************************************************************************
 * Copyright (c) 2014, 2015 IBM Corp.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Allan Stockdill-Mander - initial API and implementation and/or initial documentation
 *    Ian Craggs - convert to FreeRTOS
 *******************************************************************************/

#include "MQTTLiteOS.h"


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;
}

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);
}

int linux_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;
}


int linux_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;
}


void NetworkInit(Network* n)
{
    
    
	n->my_socket = 0;
	n->mqttread = linux_read;
	n->mqttwrite = linux_write;
}


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);
}

2.3.2 MQTTLiteOS.h

/*******************************************************************************
 * Copyright (c) 2014, 2015 IBM Corp.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Allan Stockdill-Mander - initial API and implementation and/or initial documentation
 *******************************************************************************/

#if !defined(MQTTLiteOS_H)
#define MQTTLiteOS_H


#include <sys/types.h>

#if !defined(SOCKET_ERROR)
	/** error in socket operation */
	#define SOCKET_ERROR -1
#endif

#if defined(WIN32)
/* default on Windows is 64 - increase to make Linux and Windows the same */
#define FD_SETSIZE 1024
#include <winsock2.h>
#include <ws2tcpip.h>
#define MAXHOSTNAMELEN 256
#define EAGAIN WSAEWOULDBLOCK
#define EINTR WSAEINTR
#define EINVAL WSAEINVAL
#define EINPROGRESS WSAEINPROGRESS
#define EWOULDBLOCK WSAEWOULDBLOCK
#define ENOTCONN WSAENOTCONN
#define ECONNRESET WSAECONNRESET
#define ioctl ioctlsocket
#define socklen_t int
#else
#define INVALID_SOCKET SOCKET_ERROR
#include <sys/socket.h>
#include <sys/param.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#endif

#if defined(WIN32)
#include <Iphlpapi.h>
#else
#include <sys/ioctl.h>
#include <net/if.h>
#endif

#include "ohos_init.h"
#include "cmsis_os2.h"

#include "lwip/ip_addr.h"
#include "lwip/netifapi.h"

#include "lwip/sockets.h"

#define MQTT_TASK

typedef struct Thread
{
    
    
	osThreadId_t task;
} Thread;

int ThreadStart(Thread*, void (*fn)(void*), void* arg);

typedef struct Timer
{
    
    
	struct timeval end_time;
} Timer;

typedef struct Mutex
{
    
    
	osSemaphoreId_t sem;
} Mutex;

void MutexInit(Mutex*);
int MutexLock(Mutex*);
int MutexUnlock(Mutex*);

void TimerInit(Timer*);
char TimerIsExpired(Timer*);
void TimerCountdownMS(Timer*, unsigned int);
void TimerCountdown(Timer*, unsigned int);
int TimerLeftMS(Timer*);

typedef struct Network
{
    
    
	int my_socket;
	int (*mqttread) (struct Network*, unsigned char*, int, int);
	int (*mqttwrite) (struct Network*, unsigned char*, int, int);
} Network;

int linux_read(Network*, unsigned char*, int, int);
int linux_write(Network*, unsigned char*, int, int);

 void NetworkInit(Network*);
 int NetworkConnect(Network*, char*, int);
 void NetworkDisconnect(Network*);

#endif

2.4 修改MQTTClient.c和MQTTClient.h

打开 third_party\paho_mqtt\MQTTClient-C\src\MQTTClient.c 文件，这个文件也是我们主要移植的文件，我们需要实现 socket 相关的操作，包括发送、接收数据。

2.4.1 MQTTClient.c

/*******************************************************************************
 * Copyright (c) 2014, 2017 IBM Corp.
 *
 * All rights reserved. This prog/*******************************************************************************
 * Copyright (c) 2014, 2017 IBM Corp.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *   Allan Stockdill-Mander/Ian Craggs - initial API and implementation and/or initial documentation
 *   Ian Craggs - fix for #96 - check rem_len in readPacket
 *   Ian Craggs - add ability to set message handler separately #6
 *******************************************************************************/
#include "MQTTClient.h"

#include <stdio.h>
#include <string.h>

static void NewMessageData(MessageData* md, MQTTString* aTopicName, MQTTMessage* aMessage) {
    
    
    md->topicName = aTopicName;
    md->message = aMessage;
}


static int getNextPacketId(MQTTClient *c) {
    
    
    return c->next_packetid = (c->next_packetid == MAX_PACKET_ID) ? 1 : c->next_packetid + 1;
}


static int sendPacket(MQTTClient* c, int length, Timer* timer)
{
    
    
    int rc = FAILURE,
        sent = 0;

    while (sent < length && !TimerIsExpired(timer))
    {
    
    
        rc = c->ipstack->mqttwrite(c->ipstack, &c->buf[sent], length, TimerLeftMS(timer));
        if (rc < 0)  // there was an error writing the data
            break;
        sent += rc;
    }
    if (sent == length)
    {
    
    
        TimerCountdown(&c->last_sent, c->keepAliveInterval); // record the fact that we have successfully sent the packet
        rc = SUCCESS;
    }
    else
        rc = FAILURE;
    return rc;
}


void MQTTClientInit(MQTTClient* c, Network* network, unsigned int command_timeout_ms,
		unsigned char* sendbuf, size_t sendbuf_size, unsigned char* readbuf, size_t readbuf_size)
{
    
    
    int i;
    c->ipstack = network;

    for (i = 0; i < MAX_MESSAGE_HANDLERS; ++i)
        c->messageHandlers[i].topicFilter = 0;
    c->command_timeout_ms = command_timeout_ms;
    c->buf = sendbuf;
    c->buf_size = sendbuf_size;
    c->readbuf = readbuf;
    c->readbuf_size = readbuf_size;
    c->isconnected = 0;
    c->cleansession = 0;
    c->ping_outstanding = 0;
    c->defaultMessageHandler = NULL;
	  c->next_packetid = 1;
    TimerInit(&c->last_sent);
    TimerInit(&c->last_received);
#if defined(MQTT_TASK)
	  MutexInit(&c->mutex);
#endif
}


static int decodePacket(MQTTClient* c, int* value, int timeout)
{
    
    
    unsigned char i;
    int multiplier = 1;
    int len = 0;
    const int MAX_NO_OF_REMAINING_LENGTH_BYTES = 4;

    *value = 0;
    do
    {
    
    
        int rc = MQTTPACKET_READ_ERROR;

        if (++len > MAX_NO_OF_REMAINING_LENGTH_BYTES)
        {
    
    
            rc = MQTTPACKET_READ_ERROR; /* bad data */
            goto exit;
        }
        rc = c->ipstack->mqttread(c->ipstack, &i, 1, timeout);
        if (rc != 1)
            goto exit;
        *value += (i & 127) * multiplier;
        multiplier *= 128;
    } while ((i & 128) != 0);
exit:
    return len;
}


static int readPacket(MQTTClient* c, Timer* timer)
{
    
    
    MQTTHeader header = {
    
    0};
    int len = 0;
    int rem_len = 0;

    /* 1. read the header byte.  This has the packet type in it */
    int rc = c->ipstack->mqttread(c->ipstack, c->readbuf, 1, TimerLeftMS(timer));
    if (rc != 1)
        goto exit;

    len = 1;
    /* 2. read the remaining length.  This is variable in itself */
    decodePacket(c, &rem_len, TimerLeftMS(timer));
    len += MQTTPacket_encode(c->readbuf + 1, rem_len); /* put the original remaining length back into the buffer */

    if ((unsigned int)rem_len > (c->readbuf_size - len))
    {
    
    
        rc = BUFFER_OVERFLOW;
        goto exit;
    }

    /* 3. read the rest of the buffer using a callback to supply the rest of the data */
    if (rem_len > 0 && (rc = c->ipstack->mqttread(c->ipstack, c->readbuf + len, rem_len, TimerLeftMS(timer)) != rem_len)) {
    
    
        rc = 0;
        goto exit;
    }

    header.byte = c->readbuf[0];
    rc = header.bits.type;
    if (c->keepAliveInterval > 0)
        TimerCountdown(&c->last_received, c->keepAliveInterval); // record the fact that we have successfully received a packet
exit:
    return rc;
}


// assume topic filter and name is in correct format
// # can only be at end
// + and # can only be next to separator
static char isTopicMatched(char* topicFilter, MQTTString* topicName)
{
    
    
    char* curf = topicFilter;
    char* curn = topicName->lenstring.data;
    char* curn_end = curn + topicName->lenstring.len;

    while (*curf && curn < curn_end)
    {
    
    
        if (*curn == '/' && *curf != '/')
            break;
        if (*curf != '+' && *curf != '#' && *curf != *curn)
            break;
        if (*curf == '+')
        {
    
       // skip until we meet the next separator, or end of string
            char* nextpos = curn + 1;
            while (nextpos < curn_end && *nextpos != '/')
                nextpos = ++curn + 1;
        }
        else if (*curf == '#')
            curn = curn_end - 1;    // skip until end of string
        curf++;
        curn++;
    };

    return (curn == curn_end) && (*curf == '\0');
}


int deliverMessage(MQTTClient* c, MQTTString* topicName, MQTTMessage* message)
{
    
    
    int i;
    int rc = FAILURE;

    // we have to find the right message handler - indexed by topic
    for (i = 0; i < MAX_MESSAGE_HANDLERS; ++i)
    {
    
    
        if (c->messageHandlers[i].topicFilter != 0 && (MQTTPacket_equals(topicName, (char*)c->messageHandlers[i].topicFilter) ||
                isTopicMatched((char*)c->messageHandlers[i].topicFilter, topicName)))
        {
    
    
            if (c->messageHandlers[i].fp != NULL)
            {
    
    
                MessageData md;
                NewMessageData(&md, topicName, message);
                c->messageHandlers[i].fp(&md);
                rc = SUCCESS;
            }
        }
    }

    if (rc == FAILURE && c->defaultMessageHandler != NULL)
    {
    
    
        MessageData md;
        NewMessageData(&md, topicName, message);
        c->defaultMessageHandler(&md);
        rc = SUCCESS;
    }

    return rc;
}


int keepalive(MQTTClient* c)
{
    
    
    int rc = SUCCESS;

    if (c->keepAliveInterval == 0)
        goto exit;

    // If we are waiting for a ping response, check if it has been too long
    if ( c->ping_outstanding == 1 ){
    
    
        if ( TimerIsExpired(&c->pingresp_timer) ){
    
    
            rc = FAILURE; /* PINGRESP not received in keepalive interval */
            goto exit;
        }
    }
    else{
    
    
        // If we have not sent or received anything in the timeout period,
        // send out a ping request
        if ( TimerIsExpired(&c->last_sent) || TimerIsExpired(&c->last_received) )
        {
    
    
            Timer timer;
            TimerInit(&timer);
            TimerCountdownMS(&timer, 1000);
            int len = MQTTSerialize_pingreq(c->buf, c->buf_size);
            if (len > 0 && (rc = sendPacket(c, len, &timer)) == SUCCESS){
    
     // send the ping packet
                // send the ping packet
                // Expect the PINGRESP within 2 seconds of the PINGREQ
                // being sent
                TimerCountdownMS(&c->pingresp_timer, 2000 );
                c->ping_outstanding = 1;
            }
        }
    }

exit:
    return rc;
}


void MQTTCleanSession(MQTTClient* c)
{
    
    
    int i = 0;

    for (i = 0; i < MAX_MESSAGE_HANDLERS; ++i)
        c->messageHandlers[i].topicFilter = NULL;
}


void MQTTCloseSession(MQTTClient* c)
{
    
    
    c->ping_outstanding = 0;
    c->isconnected = 0;
    if (c->cleansession)
        MQTTCleanSession(c);
}


int cycle(MQTTClient* c, Timer* timer)
{
    
    
    int len = 0,
        rc = SUCCESS;

    int packet_type = readPacket(c, timer);     /* read the socket, see what work is due */

    switch (packet_type)
    {
    
    
        default:
            /* no more data to read, unrecoverable. Or read packet fails due to unexpected network error */
            rc = packet_type;
            goto exit;
        case 0: /* timed out reading packet */
            break;
        case CONNACK:
        case PUBACK:
        case SUBACK:
        case UNSUBACK:
            break;
        case PUBLISH:
        {
    
    
            MQTTString topicName;
            MQTTMessage msg;
            int intQoS;
            msg.payloadlen = 0; /* this is a size_t, but deserialize publish sets this as int */
            if (MQTTDeserialize_publish(&msg.dup, &intQoS, &msg.retained, &msg.id, &topicName,
               (unsigned char**)&msg.payload, (int*)&msg.payloadlen, c->readbuf, c->readbuf_size) != 1)
                goto exit;
            msg.qos = (enum QoS)intQoS;
            deliverMessage(c, &topicName, &msg);
            if (msg.qos != QOS0)
            {
    
    
                if (msg.qos == QOS1)
                    len = MQTTSerialize_ack(c->buf, c->buf_size, PUBACK, 0, msg.id);
                else if (msg.qos == QOS2)
                    len = MQTTSerialize_ack(c->buf, c->buf_size, PUBREC, 0, msg.id);
                if (len <= 0)
                    rc = FAILURE;
                else
                    rc = sendPacket(c, len, timer);
                if (rc == FAILURE)
                    goto exit; // there was a problem
            }
            break;
        }
        case PUBREC:
        case PUBREL:
        {
    
    
            unsigned short mypacketid;
            unsigned char dup, type;
            if (MQTTDeserialize_ack(&type, &dup, &mypacketid, c->readbuf, c->readbuf_size) != 1)
                rc = FAILURE;
            else if ((len = MQTTSerialize_ack(c->buf, c->buf_size,
                (packet_type == PUBREC) ? PUBREL : PUBCOMP, 0, mypacketid)) <= 0)
                rc = FAILURE;
            else if ((rc = sendPacket(c, len, timer)) != SUCCESS) // send the PUBREL packet
                rc = FAILURE; // there was a problem
            if (rc == FAILURE)
                goto exit; // there was a problem
            break;
        }

        case PUBCOMP:
            break;
        case PINGRESP:
            c->ping_outstanding = 0;
            break;
    }

    if (keepalive(c) != SUCCESS) {
    
    
        //check only keepalive FAILURE status so that previous FAILURE status can be considered as FAULT
        rc = FAILURE;
    }

exit:
    if (rc == SUCCESS)
        rc = packet_type;
    else if (c->isconnected)
        MQTTCloseSession(c);
    return rc;
}


int MQTTYield(MQTTClient* c, int timeout_ms)
{
    
    
    int rc = SUCCESS;
    Timer timer;

    TimerInit(&timer);
    TimerCountdownMS(&timer, timeout_ms);

	  do
    {
    
    
        if (cycle(c, &timer) < 0)
        {
    
    
            rc = FAILURE;
            break;
        }
  	} while (!TimerIsExpired(&timer));

    return rc;
}

int MQTTIsConnected(MQTTClient* client)
{
    
    
  return client->isconnected;
}

void MQTTRun(void* parm)
{
    
    
	Timer timer;
	MQTTClient* c = (MQTTClient*)parm;

	TimerInit(&timer);

	while (1)
	{
    
    
#if defined(MQTT_TASK)
		MutexLock(&c->mutex);
#endif
		TimerCountdownMS(&timer, 500); /* Don't wait too long if no traffic is incoming */
		cycle(c, &timer);

#if defined(MQTT_TASK)
		MutexUnlock(&c->mutex);
#endif
	}
}


#if defined(MQTT_TASK)
int MQTTStartTask(MQTTClient* client)
{
    
    
	return ThreadStart(&client->thread, &MQTTRun, client);
}
#endif


int waitfor(MQTTClient* c, int packet_type, Timer* timer)
{
    
    
    int rc = FAILURE;

    do
    {
    
    
        if (TimerIsExpired(timer))
            break; // we timed out
        rc = cycle(c, timer);
    }
    while (rc != packet_type && rc >= 0);

    return rc;
}




int MQTTConnectWithResults(MQTTClient* c, MQTTPacket_connectData* options, MQTTConnackData* data)
{
    
    
    Timer connect_timer;
    int rc = FAILURE;
    MQTTPacket_connectData default_options = MQTTPacket_connectData_initializer;
    int len = 0;

#if defined(MQTT_TASK)
	  MutexLock(&c->mutex);
#endif
	  if (c->isconnected) /* don't send connect packet again if we are already connected */
		  goto exit;

    TimerInit(&connect_timer);
    TimerCountdownMS(&connect_timer, c->command_timeout_ms);

    if (options == 0)
        options = &default_options; /* set default options if none were supplied */

    c->keepAliveInterval = options->keepAliveInterval;
    c->cleansession = options->cleansession;
    TimerCountdown(&c->last_received, c->keepAliveInterval);
    if ((len = MQTTSerialize_connect(c->buf, c->buf_size, options)) <= 0)
        goto exit;
    if ((rc = sendPacket(c, len, &connect_timer)) != SUCCESS)  // send the connect packet
        goto exit; // there was a problem

    // this will be a blocking call, wait for the connack
    if (waitfor(c, CONNACK, &connect_timer) == CONNACK)
    {
    
    
        data->rc = 0;
        data->sessionPresent = 0;
        if (MQTTDeserialize_connack(&data->sessionPresent, &data->rc, c->readbuf, c->readbuf_size) == 1)
            rc = data->rc;
        else
            rc = FAILURE;
    }
    else
        rc = FAILURE;

exit:
    if (rc == SUCCESS)
    {
    
    
        c->isconnected = 1;
        c->ping_outstanding = 0;
    }

#if defined(MQTT_TASK)
	  MutexUnlock(&c->mutex);
#endif

    return rc;
}


int MQTTConnect(MQTTClient* c, MQTTPacket_connectData* options)
{
    
    
    MQTTConnackData data;
    return MQTTConnectWithResults(c, options, &data);
}


int MQTTSetMessageHandler(MQTTClient* c, const char* topicFilter, messageHandler messageHandler)
{
    
    
    int rc = FAILURE;
    int i = -1;

    /* first check for an existing matching slot */
    for (i = 0; i < MAX_MESSAGE_HANDLERS; ++i)
    {
    
    
        if (c->messageHandlers[i].topicFilter != NULL && strcmp(c->messageHandlers[i].topicFilter, topicFilter) == 0)
        {
    
    
            if (messageHandler == NULL) /* remove existing */
            {
    
    
                c->messageHandlers[i].topicFilter = NULL;
                c->messageHandlers[i].fp = NULL;
            }
            rc = SUCCESS; /* return i when adding new subscription */
            break;
        }
    }
    /* if no existing, look for empty slot (unless we are removing) */
    if (messageHandler != NULL) {
    
    
        if (rc == FAILURE)
        {
    
    
            for (i = 0; i < MAX_MESSAGE_HANDLERS; ++i)
            {
    
    
                if (c->messageHandlers[i].topicFilter == NULL)
                {
    
    
                    rc = SUCCESS;
                    break;
                }
            }
        }
        if (i < MAX_MESSAGE_HANDLERS)
        {
    
    
            c->messageHandlers[i].topicFilter = topicFilter;
            c->messageHandlers[i].fp = messageHandler;
        }
    }
    return rc;
}


int MQTTSubscribeWithResults(MQTTClient* c, const char* topicFilter, enum QoS qos,
       messageHandler messageHandler, MQTTSubackData* data)
{
    
    
    int rc = FAILURE;
    Timer timer;
    int len = 0;
    MQTTString topic = MQTTString_initializer;
    topic.cstring = (char *)topicFilter;

#if defined(MQTT_TASK)
	  MutexLock(&c->mutex);
#endif
	  if (!c->isconnected)
		    goto exit;

    TimerInit(&timer);
    TimerCountdownMS(&timer, c->command_timeout_ms);

    len = MQTTSerialize_subscribe(c->buf, c->buf_size, 0, getNextPacketId(c), 1, &topic, (int*)&qos);
    if (len <= 0)
        goto exit;
    if ((rc = sendPacket(c, len, &timer)) != SUCCESS) // send the subscribe packet
        goto exit;             // there was a problem

    if (waitfor(c, SUBACK, &timer) == SUBACK)      // wait for suback
    {
    
    
        int count = 0;
        unsigned short mypacketid;
        data->grantedQoS = QOS0;
        if (MQTTDeserialize_suback(&mypacketid, 1, &count, (int*)&data->grantedQoS, c->readbuf, c->readbuf_size) == 1)
        {
    
    
            if (data->grantedQoS != 0x80)
                rc = MQTTSetMessageHandler(c, topicFilter, messageHandler);
        }
    }
    else
        rc = FAILURE;

exit:
    if (rc == FAILURE)
        MQTTCloseSession(c);
#if defined(MQTT_TASK)
	  MutexUnlock(&c->mutex);
#endif
    return rc;
}


int MQTTSubscribe(MQTTClient* c, const char* topicFilter, enum QoS qos,
       messageHandler messageHandler)
{
    
    
    MQTTSubackData data;
    return MQTTSubscribeWithResults(c, topicFilter, qos, messageHandler, &data);
}


int MQTTUnsubscribe(MQTTClient* c, const char* topicFilter)
{
    
    
    int rc = FAILURE;
    Timer timer;
    MQTTString topic = MQTTString_initializer;
    topic.cstring = (char *)topicFilter;
    int len = 0;

#if defined(MQTT_TASK)
	  MutexLock(&c->mutex);
#endif
	  if (!c->isconnected)
		  goto exit;

    TimerInit(&timer);
    TimerCountdownMS(&timer, c->command_timeout_ms);

    if ((len = MQTTSerialize_unsubscribe(c->buf, c->buf_size, 0, getNextPacketId(c), 1, &topic)) <= 0)
        goto exit;
    if ((rc = sendPacket(c, len, &timer)) != SUCCESS) // send the subscribe packet
        goto exit; // there was a problem

    if (waitfor(c, UNSUBACK, &timer) == UNSUBACK)
    {
    
    
        unsigned short mypacketid;  // should be the same as the packetid above
        if (MQTTDeserialize_unsuback(&mypacketid, c->readbuf, c->readbuf_size) == 1)
        {
    
    
            /* remove the subscription message handler associated with this topic, if there is one */
            MQTTSetMessageHandler(c, topicFilter, NULL);
        }
    }
    else
        rc = FAILURE;

exit:
    if (rc == FAILURE)
        MQTTCloseSession(c);
#if defined(MQTT_TASK)
	  MutexUnlock(&c->mutex);
#endif
    return rc;
}


int MQTTPublish(MQTTClient* c, const char* topicName, MQTTMessage* message)
{
    
    
    int rc = FAILURE;
    Timer timer;
    MQTTString topic = MQTTString_initializer;
    topic.cstring = (char *)topicName;
    int len = 0;

#if defined(MQTT_TASK)
	  MutexLock(&c->mutex);
#endif
	  if (!c->isconnected)
		    goto exit;

    TimerInit(&timer);
    TimerCountdownMS(&timer, c->command_timeout_ms);

    if (message->qos == QOS1 || message->qos == QOS2)
        message->id = getNextPacketId(c);

    len = MQTTSerialize_publish(c->buf, c->buf_size, 0, message->qos, message->retained, message->id,
              topic, (unsigned char*)message->payload, message->payloadlen);
    if (len <= 0)
        goto exit;
    if ((rc = sendPacket(c, len, &timer)) != SUCCESS) // send the subscribe packet
        goto exit; // there was a problem

    if (message->qos == QOS1)
    {
    
    
        if (waitfor(c, PUBACK, &timer) == PUBACK)
        {
    
    
            unsigned short mypacketid;
            unsigned char dup, type;
            if (MQTTDeserialize_ack(&type, &dup, &mypacketid, c->readbuf, c->readbuf_size) != 1)
                rc = FAILURE;
        }
        else
            rc = FAILURE;
    }
    else if (message->qos == QOS2)
    {
    
    
        if (waitfor(c, PUBCOMP, &timer) == PUBCOMP)
        {
    
    
            unsigned short mypacketid;
            unsigned char dup, type;
            if (MQTTDeserialize_ack(&type, &dup, &mypacketid, c->readbuf, c->readbuf_size) != 1)
                rc = FAILURE;
        }
        else
            rc = FAILURE;
    }

exit:
    if (rc == FAILURE)
        MQTTCloseSession(c);
#if defined(MQTT_TASK)
	  MutexUnlock(&c->mutex);
#endif
    return rc;
}


int MQTTDisconnect(MQTTClient* c)
{
    
    
    int rc = FAILURE;
    Timer timer;     // we might wait for incomplete incoming publishes to complete
    int len = 0;

#if defined(MQTT_TASK)
	MutexLock(&c->mutex);
#endif
    TimerInit(&timer);
    TimerCountdownMS(&timer, c->command_timeout_ms);

	  len = MQTTSerialize_disconnect(c->buf, c->buf_size);
    if (len > 0)
        rc = sendPacket(c, len, &timer);            // send the disconnect packet
    MQTTCloseSession(c);

#if defined(MQTT_TASK)
	  MutexUnlock(&c->mutex);
#endif
    return rc;
}

2.4.2 MQTTClient.h

/*******************************************************************************
 * Copyright (c) 2014, 2017 IBM Corp.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Allan Stockdill-Mander/Ian Craggs - initial API and implementation and/or initial documentation
 *    Ian Craggs - documentation and platform specific header
 *    Ian Craggs - add setMessageHandler function
 *******************************************************************************/

#if !defined(MQTT_CLIENT_H)
#define MQTT_CLIENT_H

#if defined(__cplusplus)
 extern "C" {
    
    
#endif

#if defined(WIN32_DLL) || defined(WIN64_DLL)
  #define DLLImport __declspec(dllimport)
  #define DLLExport __declspec(dllexport)
#elif defined(LINUX_SO)
  #define DLLImport extern
  #define DLLExport  __attribute__ ((visibility ("default")))
#else
  #define DLLImport
  #define DLLExport
#endif

#include "liteOS/MQTTLiteOS.h"

#include "MQTTPacket.h"

#if defined(MQTTCLIENT_PLATFORM_HEADER)
/* The following sequence of macros converts the MQTTCLIENT_PLATFORM_HEADER value
 * into a string constant suitable for use with include.
 */
#define xstr(s) str(s)
#define str(s) #s
#include xstr(MQTTCLIENT_PLATFORM_HEADER)
#endif

#define MAX_PACKET_ID 65535 /* according to the MQTT specification - do not change! */

#if !defined(MAX_MESSAGE_HANDLERS)
#define MAX_MESSAGE_HANDLERS 5 /* redefinable - how many subscriptions do you want? */
#endif

enum QoS {
    
     QOS0, QOS1, QOS2, SUBFAIL=0x80 };

/* all failure return codes must be negative */
enum returnCode {
    
     BUFFER_OVERFLOW = -2, FAILURE = -1, SUCCESS = 0 };

/* The Platform specific header must define the Network and Timer structures and functions
 * which operate on them.
 *
typedef struct Network
{
	int (*mqttread)(Network*, unsigned char* read_buffer, int, int);
	int (*mqttwrite)(Network*, unsigned char* send_buffer, int, int);
} Network;*/

/* The Timer structure must be defined in the platform specific header,
 * and have the following functions to operate on it.  */
extern void TimerInit(Timer*);
extern char TimerIsExpired(Timer*);
extern void TimerCountdownMS(Timer*, unsigned int);
extern void TimerCountdown(Timer*, unsigned int);
extern int TimerLeftMS(Timer*);

typedef struct MQTTMessage
{
    
    
    enum QoS qos;
    unsigned char retained;
    unsigned char dup;
    unsigned short id;
    void *payload;
    size_t payloadlen;
} MQTTMessage;

typedef struct MessageData
{
    
    
    MQTTMessage* message;
    MQTTString* topicName;
} MessageData;

typedef struct MQTTConnackData
{
    
    
    unsigned char rc;
    unsigned char sessionPresent;
} MQTTConnackData;

typedef struct MQTTSubackData
{
    
    
    enum QoS grantedQoS;
} MQTTSubackData;

typedef void (*messageHandler)(MessageData*);

typedef struct MQTTClient
{
    
    
    unsigned int next_packetid,
      command_timeout_ms;
    size_t buf_size,
      readbuf_size;
    unsigned char *buf,
      *readbuf;
    unsigned int keepAliveInterval;
    char ping_outstanding;
    int isconnected;
    int cleansession;

    struct MessageHandlers
    {
    
    
        const char* topicFilter;
        void (*fp) (MessageData*);
    } messageHandlers[MAX_MESSAGE_HANDLERS];      /* Message handlers are indexed by subscription topic */

    void (*defaultMessageHandler) (MessageData*);

    Network* ipstack;
    Timer last_sent, last_received, pingresp_timer;
#if defined(MQTT_TASK)
    Mutex mutex;
    Thread thread;
#endif
} MQTTClient;

#define DefaultClient {
      
      0, 0, 0, 0, NULL, NULL, 0, 0, 0}


/**
 * Create an MQTT client object
 * @param client
 * @param network
 * @param command_timeout_ms
 * @param
 */
DLLExport void MQTTClientInit(MQTTClient* client, Network* network, unsigned int command_timeout_ms,
		unsigned char* sendbuf, size_t sendbuf_size, unsigned char* readbuf, size_t readbuf_size);

/** MQTT Connect - send an MQTT connect packet down the network and wait for a Connack
 *  The nework object must be connected to the network endpoint before calling this
 *  @param options - connect options
 *  @return success code
 */
DLLExport int MQTTConnectWithResults(MQTTClient* client, MQTTPacket_connectData* options,
    MQTTConnackData* data);

/** MQTT Connect - send an MQTT connect packet down the network and wait for a Connack
 *  The nework object must be connected to the network endpoint before calling this
 *  @param options - connect options
 *  @return success code
 */
DLLExport int MQTTConnect(MQTTClient* client, MQTTPacket_connectData* options);

/** MQTT Publish - send an MQTT publish packet and wait for all acks to complete for all QoSs
 *  @param client - the client object to use
 *  @param topic - the topic to publish to
 *  @param message - the message to send
 *  @return success code
 */
DLLExport int MQTTPublish(MQTTClient* client, const char*, MQTTMessage*);

/** MQTT SetMessageHandler - set or remove a per topic message handler
 *  @param client - the client object to use
 *  @param topicFilter - the topic filter set the message handler for
 *  @param messageHandler - pointer to the message handler function or NULL to remove
 *  @return success code
 */
DLLExport int MQTTSetMessageHandler(MQTTClient* c, const char* topicFilter, messageHandler messageHandler);

/** MQTT Subscribe - send an MQTT subscribe packet and wait for suback before returning.
 *  @param client - the client object to use
 *  @param topicFilter - the topic filter to subscribe to
 *  @param message - the message to send
 *  @return success code
 */
DLLExport int MQTTSubscribe(MQTTClient* client, const char* topicFilter, enum QoS, messageHandler);

/** MQTT Subscribe - send an MQTT subscribe packet and wait for suback before returning.
 *  @param client - the client object to use
 *  @param topicFilter - the topic filter to subscribe to
 *  @param message - the message to send
 *  @param data - suback granted QoS returned
 *  @return success code
 */
DLLExport int MQTTSubscribeWithResults(MQTTClient* client, const char* topicFilter, enum QoS, messageHandler, MQTTSubackData* data);

/** MQTT Subscribe - send an MQTT unsubscribe packet and wait for unsuback before returning.
 *  @param client - the client object to use
 *  @param topicFilter - the topic filter to unsubscribe from
 *  @return success code
 */
DLLExport int MQTTUnsubscribe(MQTTClient* client, const char* topicFilter);

/** MQTT Disconnect - send an MQTT disconnect packet and close the connection
 *  @param client - the client object to use
 *  @return success code
 */
DLLExport int MQTTDisconnect(MQTTClient* client);

/** MQTT Yield - MQTT background
 *  @param client - the client object to use
 *  @param time - the time, in milliseconds, to yield for
 *  @return success code
 */
DLLExport int MQTTYield(MQTTClient* client, int time);

/** MQTT isConnected
 *  @param client - the client object to use
 *  @return truth value indicating whether the client is connected to the server
 */
DLLExport int MQTTIsConnected(MQTTClient* client);

#if defined(MQTT_TASK)
/** MQTT start background thread for a client.  After this, MQTTYield should not be called.
*  @param client - the client object to use
*  @return success code
*/
DLLExport int MQTTStartTask(MQTTClient* client);
#endif

#if defined(__cplusplus)
     }
#endif

#endif

三、API说明

业务BUILD.gn中包含路径

include_dirs = [
        "//utils/native/lite/include",
        "//kernel/liteos_m/components/cmsis/2.0",
        "//base/iot_hardware/interfaces/kits/wifiiot_lite",
        "//foundation/communication/interfaces/kits/wifi_lite/wifiservice",
        "//vendor/hisi/hi3861/hi3861/third_party/lwip_sack/include/",
        "//third_party/paho_mqtt/MQTTPacket/src",
        "//third_party/paho_mqtt/MQTTClient-C/src",
    ]

以下网络接口位于 third_party\paho_mqtt\MQTTClient-C\src\liteOS\MQTTLiteOS.h。

3.1 NetworkInit

功能	初始化网络结构体，socket描述符、socket发送和接收函数
函数定义	void NetworkInit(Network* n)
参数	n：网络结构体
返回	无

3.2 NetworkConnect

功能	连接到指定的MQTT服务器IP、端口号
函数定义	int NetworkConnect(Network* n, char* addr, int port)
参数	n：网络结构体 addr：IP地址 port：端口
返回	0 - 成功，-1 - 失败

3.3 NetworkDisconnect

功能	关闭网络连接
函数定义	void NetworkDisconnect(Network* n)
参数	n：网络结构体
返回	无

以下 MQTT 接口位于 third_party\paho_mqtt\MQTTClient-C\src\liteOS\MQTTLiteOS.h。

3.4 MQTTClientInit

功能	创建一个MQTT客户端对象
函数定义	void MQTTClientInit(MQTTClient* c, Network* network, unsigned int command_timeout_ms, unsigned char* sendbuf, size_t sendbuf_size, unsigned char* readbuf, size_t readbuf_size)
参数	c：MQTT客户端 network：网络结构体 command_timeout_ms：超时时间 sendbuf：发送缓冲区 sendbuf_size：发送缓冲区大小 readbuf：接收缓冲区 readbuf_size：接收缓冲区大小
返回	无

3.5 MQTTConnect

功能	发送MQTT连接数据包
函数定义	int MQTTConnect(MQTTClient* c, MQTTPacket_connectData* options)
参数	c：MQTT客户端 options：连接参数
返回	错误码

3.6 MQTTPublish

功能	发送MQTT发布数据包
函数定义	int MQTTPublish(MQTTClient* c, const char* topicName, MQTTMessage* message)
参数	c：MQTT客户端 topicName：主题 message：消息
返回	错误码

3.7 MQTTSubscribe

功能	发送MQTT订阅数据包
函数定义	int MQTTSubscribe(MQTTClient* c, const char* topicFilter, enum QoS qos, messageHandler messageHandler)
参数	c：MQTT客户端 topicFilter：主题 qos：服务质量 messageHandler：消息处理函数
返回	错误码

3.8 MQTTDisconnect

功能	发送MQTT断开连接数据包并关闭连接
函数定义	int MQTTDisconnect(MQTTClient* c)
参数	c：MQTT客户端
返回	错误码

四、MQTT客户端

4.1 配置SSID和密码连接WIFI

wifi_connect.c

#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include "lwip/netif.h"
#include "lwip/netifapi.h"
#include "lwip/ip4_addr.h"
#include "lwip/api_shell.h"

#include "cmsis_os2.h"
#include "hos_types.h"
#include "wifi_device.h"
#include "wifiiot_errno.h"
#include "ohos_init.h"

#define DEF_TIMEOUT 15
#define ONE_SECOND 1

#define SELECT_WIFI_SECURITYTYPE WIFI_SEC_TYPE_PSK  

static void WiFiInit(void);
static void WaitSacnResult(void);
static int WaitConnectResult(void);
static void OnWifiScanStateChangedHandler(int state, int size);
static void OnWifiConnectionChangedHandler(int state, WifiLinkedInfo *info);
static void OnHotspotStaJoinHandler(StationInfo *info);
static void OnHotspotStateChangedHandler(int state);
static void OnHotspotStaLeaveHandler(StationInfo *info);

static int g_staScanSuccess = 0;
static int g_ConnectSuccess = 0;
static int ssid_count = 0;
WifiEvent g_wifiEventHandler = {
    
    0};
WifiErrorCode error;

#define SELECT_WLAN_PORT "wlan0"

int WifiConnect(const char *ssid, const char *psk)
{
    
    
    WifiScanInfo *info = NULL;
    unsigned int size = WIFI_SCAN_HOTSPOT_LIMIT;
    static struct netif *g_lwip_netif = NULL;

    osDelay(200);
    printf("<--System Init-->\r\n");

    //初始化WIFI
    WiFiInit();

    //使能WIFI
    if (EnableWifi() != WIFI_SUCCESS)
    {
    
    
        printf("EnableWifi failed, error = %d\r\n", error);
        return -1;
    }

    //判断WIFI是否激活
    if (IsWifiActive() == 0)
    {
    
    
        printf("Wifi station is not actived.\r\n");
        return -1;
    }

    //分配空间，保存WiFi信息
    info = malloc(sizeof(WifiScanInfo) * WIFI_SCAN_HOTSPOT_LIMIT);
    if (info == NULL)
    {
    
    
        return -1;
    }
    //轮询查找WiFi列表
    do{
    
    
        //重置标志位
        ssid_count = 0;
        g_staScanSuccess = 0;

        //开始扫描
        Scan();

        //等待扫描结果
        WaitSacnResult();

        //获取扫描列表
        error = GetScanInfoList(info, &size);

    }while(g_staScanSuccess != 1);
    //打印WiFi列表
    printf("********************\r\n");
    for(uint8_t i = 0; i < ssid_count; i++)
    {
    
    
        printf("no:%03d, ssid:%-30s, rssi:%5d\r\n", i+1, info[i].ssid, info[i].rssi/100);
    }
    printf("********************\r\n");
    
    //连接指定的WiFi热点
    for(uint8_t i = 0; i < ssid_count; i++)
    {
    
    
        if (strcmp(ssid, info[i].ssid) == 0)
        {
    
    
            int result;

            printf("Select:%3d wireless, Waiting...\r\n", i+1);

            //拷贝要连接的热点信息
            WifiDeviceConfig select_ap_config = {
    
    0};
            strcpy(select_ap_config.ssid, info[i].ssid);
            strcpy(select_ap_config.preSharedKey, psk);
            select_ap_config.securityType = SELECT_WIFI_SECURITYTYPE;

            if (AddDeviceConfig(&select_ap_config, &result) == WIFI_SUCCESS)
            {
    
    
                if (ConnectTo(result) == WIFI_SUCCESS && WaitConnectResult() == 1)
                {
    
    
                    printf("WiFi connect succeed!\r\n");
                    g_lwip_netif = netifapi_netif_find(SELECT_WLAN_PORT);
                    break;
                }
            }
        }

        if(i == ssid_count-1)
        {
    
    
            printf("ERROR: No wifi as expected\r\n");
            while(1) osDelay(100);
        }
    }
     //启动DHCP
    if (g_lwip_netif)
    {
    
    
        dhcp_start(g_lwip_netif);
        printf("begain to dhcp\r\n");
    }


    //等待DHCP
    for(;;)
    {
    
    
        if(dhcp_is_bound(g_lwip_netif) == ERR_OK)
        {
    
    
            printf("<-- DHCP state:OK -->\r\n");

            //打印获取到的IP信息
            netifapi_netif_common(g_lwip_netif, dhcp_clients_info_show, NULL);
            break;
        }

        printf("<-- DHCP state:Inprogress -->\r\n");
        osDelay(100);
    }

    osDelay(100);

    return 0;
}

static void WiFiInit(void)
{
    
    
    printf("<--Wifi Init-->\r\n");
    g_wifiEventHandler.OnWifiScanStateChanged = OnWifiScanStateChangedHandler;
    g_wifiEventHandler.OnWifiConnectionChanged = OnWifiConnectionChangedHandler;
    g_wifiEventHandler.OnHotspotStaJoin = OnHotspotStaJoinHandler;
    g_wifiEventHandler.OnHotspotStaLeave = OnHotspotStaLeaveHandler;
    g_wifiEventHandler.OnHotspotStateChanged = OnHotspotStateChangedHandler;
    error = RegisterWifiEvent(&g_wifiEventHandler);
    if (error != WIFI_SUCCESS)
    {
    
    
        printf("register wifi event fail!\r\n");
    }
    else
    {
    
    
        printf("register wifi event succeed!\r\n");
    }
}

static void OnWifiScanStateChangedHandler(int state, int size)
{
    
    
    if (size > 0)
    {
    
    
        ssid_count = size;
        g_staScanSuccess = 1;
    }
    printf("callback function for wifi scan:%d, %d\r\n", state, size);
    return;
}

static void OnWifiConnectionChangedHandler(int state, WifiLinkedInfo *info)
{
    
    
    if (info == NULL)
    {
    
    
        printf("WifiConnectionChanged:info is null, stat is %d.\n", state);
    }
    else
    {
    
    
        if (state == WIFI_STATE_AVALIABLE)
        {
    
    
            g_ConnectSuccess = 1;
        }
        else
        {
    
    
            g_ConnectSuccess = 0;
        }
    }
}

static void OnHotspotStaJoinHandler(StationInfo *info)
{
    
    
    (void)info;
    printf("STA join AP\n");
    return;
}

static void OnHotspotStaLeaveHandler(StationInfo *info)
{
    
    
    (void)info;
    printf("HotspotStaLeave:info is null.\n");
    return;
}

static void OnHotspotStateChangedHandler(int state)
{
    
    
    printf("HotspotStateChanged:state is %d.\n", state);
    return;
}

static void WaitSacnResult(void)
{
    
    
    int scanTimeout = DEF_TIMEOUT;
    while (scanTimeout > 0)
    {
    
    
        sleep(ONE_SECOND);
        scanTimeout--;
        if (g_staScanSuccess == 1)
        {
    
    
            printf("WaitSacnResult:wait success[%d]s\n", (DEF_TIMEOUT - scanTimeout));
            break;
        }
    }
    if (scanTimeout <= 0)
    {
    
    
        printf("WaitSacnResult:timeout!\n");
    }
}

static int WaitConnectResult(void)
{
    
    
    int ConnectTimeout = DEF_TIMEOUT;
    while (ConnectTimeout > 0)
    {
    
    
        sleep(ONE_SECOND);
        ConnectTimeout--;
        if (g_ConnectSuccess == 1)
        {
    
    
            printf("WaitConnectResult:wait success[%d]s\n", (DEF_TIMEOUT - ConnectTimeout));
            break;
        }
    }
    if (ConnectTimeout <= 0)
    {
    
    
        printf("WaitConnectResult:timeout!\n");
        return 0;
    }

    return 1;
}

wifi_connect.h

#ifndef __WIFI_CONNECT_H__
#define __WIFI_CONNECT_H__

int WifiConnect(const char *ssid,const char *psk);

#endif /* __WIFI_CONNECT_H__ */

4.2 网络初始化

Network network;
//初始化结构体
NetworkInit(&network);
//连接到指定的MQTT服务器IP、端口号
NetworkConnect(&network, "192.168.31.225", 1883); // 修改为要连接的电脑IP

4.3 设置MQTT缓存

static unsigned char sendBuf[1000];
static unsigned char readBuf[1000];

MQTTClient client;

MQTTClientInit(&client, &network, 2000, sendBuf, sizeof(sendBuf), readBuf, sizeof(readBuf));

4.4 设置MQTT相关参数并连接MQTT服务器

MQTTString clientId = MQTTString_initializer;
clientId.cstring = "bearpi";

MQTTPacket_connectData data = MQTTPacket_connectData_initializer;
data.clientID          = clientId;
data.willFlag          = 0;
data.MQTTVersion       = 3;
data.keepAliveInterval = 0;
data.cleansession      = 1;

printf("MQTTConnect  ...\n");
rc = MQTTConnect(&client, &data);

4.5 订阅主题和接收消息

void messageArrived(MessageData* data)
{
    
    
	printf("Message arrived on topic %.*s: %.*s\n", data->topicName->lenstring.len, data->topicName->lenstring.data,
		data->message->payloadlen, data->message->payload);
}

printf("MQTTSubscribe  ...\n");
rc = MQTTSubscribe(&client, "substopic", 2, messageArrived);

4.6 发送消息

MQTTMessage message;
char payload[30];

message.qos = 2;
message.retained = 0;
message.payload = payload;
sprintf(payload, "message number %d", count);
message.payloadlen = strlen(payload);

rc = MQTTPublish(&client, "pubtopic", &message);

4.7 完整代码

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include "ohos_init.h"
#include "cmsis_os2.h"

#include "wifi_connect.h"
#include "MQTTClient.h"




static unsigned char sendBuf[1000];
static unsigned char readBuf[1000];

Network network;

void messageArrived(MessageData* data)
{
    
    
	printf("Message arrived on topic %.*s: %.*s\n", data->topicName->lenstring.len, data->topicName->lenstring.data,
		data->message->payloadlen, data->message->payload);
}

/* */

static void MQTT_DemoTask(void)
{
    
    
	WifiConnect("test","12345678");  // 修改为要连接的WIFI
	printf("Starting ...\n");
	int rc, count = 0;
	MQTTClient client;

	NetworkInit(&network);
	printf("NetworkConnect  ...\n");
begin:	
	NetworkConnect(&network, "192.168.31.225", 1883);// 修改为要连接的电脑IP
	printf("MQTTClientInit  ...\n");
	MQTTClientInit(&client, &network, 2000, sendBuf, sizeof(sendBuf), readBuf, sizeof(readBuf));

	MQTTString clientId = MQTTString_initializer;
	clientId.cstring = "bearpi";

	MQTTPacket_connectData data = MQTTPacket_connectData_initializer;
  	data.clientID          = clientId;
	data.willFlag          = 0;
	data.MQTTVersion       = 3;
	data.keepAliveInterval = 0;
	data.cleansession      = 1;

	printf("MQTTConnect  ...\n");
	rc = MQTTConnect(&client, &data);
	if (rc != 0) {
    
    
		printf("MQTTConnect: %d\n", rc);
		NetworkDisconnect(&network);
		MQTTDisconnect(&client);
		osDelay(200);
		goto begin;
	}

	printf("MQTTSubscribe  ...\n");
	rc = MQTTSubscribe(&client, "substopic", 2, messageArrived);
	if (rc != 0) {
    
    
		printf("MQTTSubscribe: %d\n", rc);
		osDelay(200);
		goto begin;
	}
	while (++count)
	{
    
    
		MQTTMessage message;
		char payload[30];

		message.qos = 2;
		message.retained = 0;
		message.payload = payload;
		sprintf(payload, "message number %d", count);
		message.payloadlen = strlen(payload);

		if ((rc = MQTTPublish(&client, "pubtopic", &message)) != 0){
    
    
			printf("Return code from MQTT publish is %d\n", rc);
			NetworkDisconnect(&network);
			MQTTDisconnect(&client);
			goto begin;
		}
		osDelay(50);	
	}
}
static void MQTT_Demo(void)
{
    
    
    osThreadAttr_t attr;

    attr.name = "MQTT_DemoTask";
    attr.attr_bits = 0U;
    attr.cb_mem = NULL;
    attr.cb_size = 0U;
    attr.stack_mem = NULL;
    attr.stack_size = 10240;
    attr.priority = osPriorityNormal;

    if (osThreadNew((osThreadFunc_t)MQTT_DemoTask, NULL, &attr) == NULL) {
    
    
        printf("[MQTT_Demo] Falied to create MQTT_DemoTask!\n");
    }
}

APP_FEATURE_INIT(MQTT_Demo);

五、搭建本地MQTT服务器

EMQ官网下载：https://www.emqx.com/zh/downloads?product=broker

• 下载EMQ X开源版
  
• 解压后进入 emqx-windows-4.3.8\emqx\bin 目录（路径不要带有空格或中文）
  
• Shift+右键在此处打开 Powershell 窗口，输入命令 emqx start
  
• 打开浏览器，输入 http://127.0.0.1:18083/，账号 admin，密码 public，进入管理界面
  
• 工具 - Websocket，选择连接
  
• 订阅主题和发布消息
  

六、运行测试

调试打印：

服务器查看：

---

• 由 Leung 写于 2021 年 4 月 4 日

• 参考：【鸿蒙2.0设备开发教程】小熊派HarmonyOS 鸿蒙·季 开发教程
　　　　OpenHarmony轻量系统开发【11】移植MQTT
　　　　在鸿蒙系统上使用MQTT编程