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如何在鸿蒙系统中移植 paho mqtt去实现MQTT协议

发布于 2020-10-23 阅读 97
  • 物联网
  • 源码
  • 鸿蒙OS
原创

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。

相关源码已经打包上传,顺便上传了一个测试OK的固件,大家可以直接下载附件直接测试。解压后会得到5个压缩包,继续解压即可

图片.png

3.9.1 MQTT介绍

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

图片.png

3.9.2 移植 paho mqtt软件包

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:
图片.png

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,目录结构大致如下:

图片.png

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",
        "MQTTPacket/samples",
        "//vendor/hisi/hi3861/hi3861/third_party/lwip_sack/include",
        "//kernel/liteos_m/components/cmsis/2.0",
    ]
}


pahomqtt_sources = [
"MQTTPacket/samples/transport.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 = [
        "//third_party/pahomqtt"
    ]
}

2. 让hi3861编译的时候,编译 paho mqtt软件包

打开vendor\hisi\hi3861\hi3861\BUILD.gn 文件,在lite_component(“sdk”) 中增加 “//third_party/pahomqtt:pahomqtt_static”,

修改后文件内容如下:
图片.png

完成以上修改后,就可以开始编译了,然而很不幸的。。。你会发现好多编译报错。

不过没事,我们来一个一个解决。

3. 移植,修改编译报错

打开 third_party\pahomqtt\MQTTPacket\samples\transport.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。其实移植就3步。

(1)首先我们导入几个头文件

#include "lwip/netifapi.h"

#include "lwip/sockets.h"

(2)其次修改 transport_sendPacketBuffer 函数,内容修改后如下:

int transport_sendPacketBuffer(int sock, unsigned char* buf, int buflen)
{
	int rc = 0;
	rc = send(sock, buf, buflen, 0);
	return rc;
}

(3)后面编译的时候会报错说 close 函数不存在,我们修改 transport_close 函数,修改后内容如下:

{
int rc;

	rc = shutdown(sock, SHUT_WR);
	rc = recv(sock, NULL, (size_t)0, 0);
	rc = lwip_close(sock);

	return rc;
}

(4)修改完 transport.c 文件后,大家编译的时候估计会遇到很多编译错误,都是某个局部变量未使用那种,大家可以修改就行。

类似于这样的,提示 buflen 未使用的错误,大家只需要在代码中随便写个buflen = buflen ; 即可。
图片.png

3.9.3 编写测试代码

测试代码比较好写。主要是3个文件,内容我都贴出来了:

图片.png

(1)BUILD.gn文件内容:

# 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.

static_library("mqtt_test_at") {
    sources = [
        "mqtt_test.c",
        "at_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/MQTTPacket/samples",
        "//vendor\hisi\hi3861\hi3861\components\at\src"
    ]
}

(2)at_entry.c文件主要是注册了一个AT指令,后面大家可以使用 AT+MQTTTEST 指令来测试MQTT功能。代码内容如下:


#include <unistd.h>

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

#include <unistd.h>

#include <at.h>
#include <hi_at.h>

#include "hi_wifi_api.h"


#include "mqtt_test.h"


void mqtt_test_thread(void * argv)
{
    argv = argv;

    mqtt_test();

}

hi_u32 at_exe_mqtt_test_cmd(void)
{
    osThreadAttr_t attr;

    attr.name = "wifi_config_thread";
    attr.attr_bits = 0U;
    attr.cb_mem = NULL;
    attr.cb_size = 0U;
    attr.stack_mem = NULL;
    attr.stack_size = 4096;
    attr.priority = 36;

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

    AT_RESPONSE_OK;
    return HI_ERR_SUCCESS;
}

const at_cmd_func g_at_mqtt_func_tbl[] = {
    {"+MQTTTEST", 9, HI_NULL, HI_NULL, HI_NULL, (at_call_back_func)at_exe_mqtt_test_cmd},
};

void AtExampleEntry(void)
{
    hi_at_register_cmd(g_at_mqtt_func_tbl, sizeof(g_at_mqtt_func_tbl)/sizeof(g_at_mqtt_func_tbl[0]));
}

SYS_RUN(AtExampleEntry);

(3)mqtt_test.c 文件则是编写了一个简单的MQTT测试代码

,具体代码讲解,后面会重新开一篇。其中测试用的mqtt服务器是我自己的服务器:106.13.62.194

大家也可以改成自己的,也可以直接用我个人的mqtt服务器。


#include <unistd.h>

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

#include <unistd.h>
#include "hi_wifi_api.h"
//#include "wifi_sta.h"
#include "lwip/ip_addr.h"
#include "lwip/netifapi.h"

#include "lwip/sockets.h"

#include "MQTTPacket.h"
#include "transport.h"

int toStop = 0;

int mqtt_connect(void)
{
	MQTTPacket_connectData data = MQTTPacket_connectData_initializer;
	int rc = 0;
	int mysock = 0;
	unsigned char buf[200];
	int buflen = sizeof(buf);
	int msgid = 1;
	MQTTString topicString = MQTTString_initializer;
	int req_qos = 0;
	char* payload = "hello HarmonyOS";
	int payloadlen = strlen(payload);
	int len = 0;
	char *host = "106.13.62.194";
    //char *host = "192.168.1.102";
	int port = 1883;


	mysock = transport_open(host, port);
	if(mysock < 0)
		return mysock;

	printf("Sending to hostname %s port %d\n", host, port);

	data.clientID.cstring = "me";
	data.keepAliveInterval = 20;
	data.cleansession = 1;
	data.username.cstring = "testuser";
	data.password.cstring = "testpassword";

	len = MQTTSerialize_connect(buf, buflen, &data);
	rc = transport_sendPacketBuffer(mysock, buf, len);

	/* 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);
			goto exit;
		}
	}
	else
		goto exit;

	/* subscribe */
	topicString.cstring = "substopic";
	len = MQTTSerialize_subscribe(buf, buflen, 0, msgid, 1, &topicString, &req_qos);
	rc = transport_sendPacketBuffer(mysock, buf, len);
	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);
			goto exit;
		}
	}
	else
		goto exit;

	/* loop getting msgs on subscribed topic */
	topicString.cstring = "pubtopic";
	while (!toStop)
	{
		/* transport_getdata() has a built-in 1 second timeout,
		your mileage will vary */
		if (MQTTPacket_read(buf, buflen, transport_getdata) == PUBLISH)
		{
			unsigned char dup;
			int qos;
			unsigned char retained;
			unsigned short msgid;
			int payloadlen_in;
			unsigned char* payload_in;
			int rc;
			MQTTString receivedTopic;
			rc = MQTTDeserialize_publish(&dup, &qos, &retained, &msgid, &receivedTopic,
					&payload_in, &payloadlen_in, buf, buflen);
			printf("message arrived %.*s\n", payloadlen_in, payload_in);

            rc = rc;
        }

		printf("publishing reading\n");
		len = MQTTSerialize_publish(buf, buflen, 0, 0, 0, 0, topicString, (unsigned char*)payload, payloadlen);
        rc = transport_sendPacketBuffer(mysock, buf, len);
	}

	printf("disconnecting\n");
	len = MQTTSerialize_disconnect(buf, buflen);
	rc = transport_sendPacketBuffer(mysock, buf, len);
exit:
	transport_close(mysock);

    rc = rc;

	return 0;
}


void mqtt_test(void)
{
    mqtt_connect();
}

mqtt_test.h文件内容:

#define __MQTT_TEST_H__

void mqtt_test(void);

#endif /* __MQTT_TEST_H__ */

到这里就完成了代码部分,可以开始编译了。

3.9.4 MQTT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:

图片.png

弄完后打开软件,按图操作:
图片.png

操作完后,我们把编译后程序烧写到开发板,输入如下串口指令,让开发板连接上网络,因为MQTT功能需要网络支持。输入如下串口指令:


AT+CONN="12-203",,2,"07686582488"               连接到路由器,注意wifi热点名和密码用自己的

AT+DHCP=wlan0,1                                              获取IP地址

AT+IFCFG                                                             打印查看IP地址

串口指令的应答应该如下:
图片.png

成功连接上路由器后,请确保路由器是可以上网的。

然后我们输入我们的 MQTT测试的AT指令: AT+MQTTTEST

应该可以看到如下打印:

图片.png

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 pubtopic,消息内容为 hello HarmonyOS ! ,说明实验成功。

图片.png

3.9.5 总结

这一次的内容比较多,其中总结起来就4步:

(1)添加第三方软件包 paho mqtt,关于如何添加第3方软件包,我之前有一篇文章已经讲了。

可以参考:如何往鸿蒙系统源码中添加第三方软件包

(2)移植 paho mqtt

(3)编写测试代码,这里我们用的是注册AT指令的方式,方便大家使用AT指令测试。

(4)测试,这里用电脑装mqtt客户端程序,去验证。

作者:连志安

获取原文相关源代码及软件资源包

转自https://harmonyos.51cto.com/posts/1384?sdk

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