使用SDK接入

KLink MQTT基于MQTT协议之上进行数据格式定义，设备开发者可以参考KLink与MQTT协议开源实现Eclipse Paho自主开发。

准备工作： 在IoT OS后台创建MQTT协议登录不校验产品并创建设备。

• 1.用户可在github获取paho.mqtt.c开源实现，使用gcc编译客户端，操作如下：

    git clone https://github.com/eclipse/paho.mqtt.c.git

    cd paho.mqtt.c

    make

• 2.进入samples文件夹编辑修改MQTTClient_publish.c文件（修改连接IP、clientid、topic见注释）

    /*******************************************************************************
     * 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 <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include "MQTTClient.h"
  
    #define ADDRESS "test-mqtt.hekr.me:1883"//定义MQTT设备对接域名与端口
    #define CLIENTID"dev:{pk}:{devId}"//定义客户端链接识别码，参数之间用：隔开，括号中填入平台上创建的产品PK和设备ID，括号为占位符，参数填入后请删除括号
    #define TOPIC   "up/dev/{pk}/{devId}"//定义数据发布主题，括号中填入平台上创建的产品PK和设备ID，括号为占位符，参数填入后请删除括号
    #define PAYLOAD "Hello World!"//定义上报内容
    #define QOS 1
    #define TIMEOUT 10000L
  
    int main(int argc, char* argv[])
    {
    MQTTClient client;
    MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
    MQTTClient_message pubmsg = MQTTClient_message_initializer;
    MQTTClient_deliveryToken token;
    int rc;
  
    MQTTClient_create(&client, ADDRESS, CLIENTID,
    MQTTCLIENT_PERSISTENCE_NONE, NULL);
    conn_opts.keepAliveInterval = 20;
    conn_opts.cleansession = 1;
  
    if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
    {
    printf("Failed to connect, return code %d\n", rc);
    exit(EXIT_FAILURE);
    }
    pubmsg.payload = PAYLOAD;
    pubmsg.payloadlen = (int)strlen(PAYLOAD);
    pubmsg.qos = QOS;
    pubmsg.retained = 0;
    MQTTClient_publishMessage(client, TOPIC, &pubmsg, &token);
    printf("Waiting for up to %d seconds for publication of %s\n"
    "on topic %s for client with ClientID: %s\n",
    (int)(TIMEOUT/1000), PAYLOAD, TOPIC, CLIENTID);
    rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);
    printf("Message with delivery token %d delivered\n", token);
    MQTTClient_disconnect(client, 10000);
    MQTTClient_destroy(&client);
    return rc;
    }
  

• 3.在sample目录用以下命令进行编译：

    gcc -I../ -L../../../paho.mqtt.c/build/output/ MQTTClient_subscribe.c -lpaho-mqtt3c -o MQTTTest -lrt

• 4.编译完成后运行可执行文件：

  ./MQTTTest

• 5.成功运行后可在IoT OS后台上下行数据中查询到相关设备的登录信息和数据上报信息。

注： 若在IoT OS后台创建的是MQTT协议登录需校验产品，则2.2中的代码需要在44行后增加两行：

conn_opts.username = &USERNAME;//定义MQTT登录用户名
conn_opts.password = &PASSWORD;//定义MQTT登录用户密码

【注】其中的USERNAME与PASSWORD需根据对应校验规则进行拼接计算，计算方式参考。