mqtt C语言版本,MQTT客户端编程--C语言
环境准备php
①安装paho c库html
解压
tar zxvf paho.mqtt.c-1.3.0.tar.gzgithub
cd paho.mqtt.c-1.3.0服务器
编译session
# make多线程
在paho.mqtt.c-1.3.0/build/output下能够找到以下的输出文件：app
# make installeclipse
库将被安装到/usr/local/lib中，须要把库的路径增长到/etc/ld.so.conf。而后执行ldconfig使配置生效异步
测试：
建立客户端的步骤：
1.建立一个客户端对象；
2.设置链接MQTT服务器的选项；
3.若是多线程(异步模式)操做被使用则设置回调函数(详见 Asynchronous >vs synchronous client applications)；
4.订阅客户端须要接收的任意话题；
5.重复如下操做直到结束：
a.发布客户端须要的任意信息；
b.处理全部接收到的信息；
6.断开客户端链接；
7.释放客户端使用的全部内存。
咱们使用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。将如下的代码更改：
#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
若是你的MQTT服务器不容许匿名访问，则还须要添加姓名和密码：
char *username= "user"; //用户名
char *password = "test"; //密码
并将用户名和密码写入链接选项中：
conn_opts.username = username; //将用户名写入链接选项中
conn_opts.password = password; //将密码写入链接选项中
添加的代码具体位置详细查看代码，更改后的代码以下所示：
/*******************************************************************************
* 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 confirmed\n", dt);
deliveredtoken = dt;
}
int msgarrvd(void *context, char *topicName, int topicLen, MQTTClient_message *message)
{
int i;
char* payloadptr;
printf("Message arrived\n");
printf(" topic: %s\n", topicName);
printf(" message: ");
payloadptr = message->payload;
for(i=0; ipayloadlen; i++)
{
putchar(*payloadptr++);
}
putchar('\n');
MQTTClient_freeMessage(&message);
MQTTClient_free(topicName);
return 1;
}
void connlost(void *context, char *cause)
{
printf("\nConnection lost\n");
printf(" cause: %s\n", cause);
}
int main(int argc, char* argv[])
{
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
int rc;
int ch;
MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE, NULL);
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd, delivered);
if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
exit(EXIT_FAILURE);
}
printf("Subscribing to topic %s\nfor client %s using QoS%d\n\n"
"Press Q to quit\n\n", TOPIC, CLIENTID, QOS);
MQTTClient_subscribe(client, TOPIC, QOS);
do
{
ch = getchar();
} while(ch!='Q' && ch != 'q');
MQTTClient_unsubscribe(client, TOPIC);
MQTTClient_disconnect(client, 10000);
MQTTClient_destroy(&client);
return rc;
}
更改完成以后回到paho.mqtt.c-1.3.0目录，执行make编译出bin文件
进入paho.mqtt.c-1.3.0/build/output/samples，看到从新编译生成的MQTTClient_scribe ，执行如下命令：
./MQTTClient_subscribe
同时开启一个发布端发布消息，观察该应用是否能正常接收到消息
输出如下结果：
