mqtt客户端编程c语言,MQTT客户端编程C语言Go语言中文社区

环境准备

①安装paho c库

解压

tar zxvf paho.mqtt.c-1.3.0.tar.gz

cd paho.mqtt.c-1.3.0

编译

# make

在paho.mqtt.c-1.3.0/build/output下可以找到如下的输出文件&＃xff1a;

# make install

库将被安装到/usr/local/lib中&＃xff0c;需要把库的路径增加到/etc/ld.so.conf。然后执行ldconfig使配置生效

测试&＃xff1a;

创建客户端的步骤&＃xff1a;

1.创建一个客户端对象&＃xff1b;

2.设置连接MQTT服务器的选项&＃xff1b;

3.如果多线程(异步模式)操作被使用则设置回调函数(详见 Asynchronous >vs synchronous client applications)&＃xff1b;

4.订阅客户端需要接收的任意话题&＃xff1b;

5.重复以下操作直到结束&＃xff1a;

a.发布客户端需要的任意信息&＃xff1b;

b.处理所有接收到的信息&＃xff1b;

6.断开客户端连接&＃xff1b;

7.释放客户端使用的所有内存。

我们使用Paho自带的示例程序。打开paho.mqtt.c-1.3.0/src/samples下的MQTTClient_subscribe .c文件。将以下的代码更改&＃xff1a;

#define ADDRESS "tcp://192.168.43.128:1883"

#define CLIENTID "ExampleClientSub"

#define TOPIC "MQTT Examples"

#define PAYLOAD "Hello World!"

#define QOS 1

#define TIMEOUT 10000L

如果你的MQTT服务器不允许匿名访问&＃xff0c;则还需要添加姓名和密码&＃xff1a;

char *username&＃61; "user"; //用户名

char *password &＃61; "test"; //密码

并将用户名和密码写入连接选项中&＃xff1a;conn_opts.username &＃61; username; //将用户名写入连接选项中

conn_opts.password &＃61; password; //将密码写入连接选项中

添加的代码具体位置详细查看代码&＃xff0c;更改后的代码如下所示&＃xff1a;/*******************************************************************************

* Copyright (c) 2012, 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:

* Ian Craggs - initial contribution

*******************************************************************************/

#include

#include

#include

#include "MQTTClient.h"

#define ADDRESS "tcp://192.168.43.128:1883"

#define CLIENTID "ExampleClientSub"

#define TOPIC "MQTT Examples"

#define PAYLOAD "Hello World!"

#define QOS 1

#define TIMEOUT 10000L

volatile MQTTClient_deliveryToken deliveredtoken;

void delivered(void *context, MQTTClient_deliveryToken dt)

{

printf("Message with token value %d delivery confirmedn", dt);

deliveredtoken &＃61; dt;

}

int msgarrvd(void *context, char *topicName, int topicLen, MQTTClient_message *message)

{

int i;

char* payloadptr;

printf("Message arrivedn");

printf(" topic: %sn", topicName);

printf(" message: ");

payloadptr &＃61; message->payload;

for(i&＃61;0; ipayloadlen; i&＃43;&＃43;)

{

putchar(*payloadptr&＃43;&＃43;);

}

putchar(&＃39;n&＃39;);

MQTTClient_freeMessage(&message);

MQTTClient_free(topicName);

return 1;

}

void connlost(void *context, char *cause)

{

printf("nConnection lostn");

printf(" cause: %sn", cause);

}

int main(int argc, char* argv[])

{

MQTTClient client;

MQTTClient_connectOptions conn_opts &＃61; MQTTClient_connectOptions_initializer;

int rc;

int ch;

MQTTClient_create(&client, ADDRESS, CLIENTID,

MQTTCLIENT_PERSISTENCE_NONE, NULL);

conn_opts.keepAliveInterval &＃61; 20;

conn_opts.cleansession &＃61; 1;

MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd, delivered);

if ((rc &＃61; MQTTClient_connect(client, &conn_opts)) !&＃61; MQTTCLIENT_SUCCESS)

{

printf("Failed to connect, return code %dn", rc);

exit(EXIT_FAILURE);

}

printf("Subscribing to topic %snfor client %s using QoS%dnn"

"Press Q to quitnn", TOPIC, CLIENTID, QOS);

MQTTClient_subscribe(client, TOPIC, QOS);

do

{

ch &＃61; getchar();

} while(ch!&＃61;&＃39;Q&＃39; && ch !&＃61; &＃39;q&＃39;);

MQTTClient_unsubscribe(client, TOPIC);

MQTTClient_disconnect(client, 10000);

MQTTClient_destroy(&client);

return rc;

}

更改完成之后回到paho.mqtt.c-1.3.0目录&＃xff0c;执行make编译出bin文件

进入paho.mqtt.c-1.3.0/build/output/samples&＃xff0c;看到重新编译生成的MQTTClient_scribe &＃xff0c;执行以下命令&＃xff1a;

./MQTTClient_subscribe

同时开启一个发布端发布消息&＃xff0c;观察该应用是否能正常接收到消息

输出以下结果&＃xff1a;