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      Cloud IoT Core example codes
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        Contents

        Cloud IoT Core example codes

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          Article Summary

          Available in Classic and VPC

          This page provides example codes for publishing messages and subscribing to the Cloud IoT Core server based on the MQTT protocol, using certificates downloaded from the Cloud IoT Core console.

          Java

          An example code to access Cloud IoT Core, repeat publish and subscribe messages 5 times, and end the program. The messages are published on the factory/room1/temperature topic, and the alert topic, which is republished through Cloud IoT core, is subscribed.

          Settings

          MQTT and TLS libraries are required to run example file.

          • maven
          <dependencies>
  <dependency>
    <groupId>org.eclipse.paho</groupId>
    <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
    <version>${version}</version>
  </dependency>
  <dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcpkix-jdk15on</artifactId>
    <version>${version}</version>
  </dependency>
</dependencies>
          • gradle
          implementation 'org.eclipse.paho:org.eclipse.paho.client.mqttv3:${version}'
implementation 'org.bouncycastle:bcpkix-jdk15on:${version}'

          Example code

          The Java example code is as follows:

          import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.openssl.PEMKeyPair;
import org.bouncycastle.openssl.PEMParser;
import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

import javax.net.ssl.KeyManagerFactory;
import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManagerFactory;
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.IOException;
import java.security.*;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.List;


public class MqttExample {

    public static void main(String[] args) throws Exception {
        String clientId = "myClientTest";

        /*
         *** Modify file path and server ***
         */
        // MQTT server hostname
        String iotServer = "ssl://msg01.cloudiot.ntruss.com";

        String rootCaCertFilePath = "/<Your>/<file>/<path>/rootCaCert.pem";
        String clientCaChainFilePath = "/<Your>/<file>/<path>/caChain.pem";
        String clientCertFilePath = "/<Your>/<file>/<path>/cert.pem";
        String clientKeyFilePath = "/<Your>/<file>/<path>/private.pem";
        String password = "";

        /*
        Make Root CA TrustManager and Client Keystore
         */
        MqttExample mqttExample = new MqttExample();
        // CA certificate is used to **authenticate server**
        TrustManagerFactory tmf = mqttExample.getTrustManagerFactory(rootCaCertFilePath);

        // client key, certificates and cachain are sent to server to authenticate client
        KeyManagerFactory kmf = mqttExample.getKeyManagerFactory(clientCaChainFilePath, clientCertFilePath, clientKeyFilePath, password);


        /*
        MQTT Connection
         */

        // Set MQTT Client
        MqttClient mqttClient = new MqttClient(iotServer, clientId, new MemoryPersistence());
        MqttConnectOptions connOpts = new MqttConnectOptions();
        connOpts.setCleanSession(true);
        connOpts.setConnectionTimeout(60);
        connOpts.setKeepAliveInterval(60);
        connOpts.setMqttVersion(MqttConnectOptions.MQTT_VERSION_3_1);

        // create SSL socket factory
        SSLContext context = SSLContext.getInstance("TLSv1.2");
        context.init(kmf.getKeyManagers(), tmf.getTrustManagers(), null);
        connOpts.setSocketFactory(context.getSocketFactory());
        mqttClient.connect(connOpts);

        System.out.println("=== Successfully Connected");


        /*
        Subscribe & Publish Message
        Publish message on the device ---> IoT Platform(alert republish action) ---> Subscribe message on the device
         */

        mqttClient.setCallback(new MqttCallback() {
            public void connectionLost(Throwable throwable) {
                System.out.println("=== Connection lost.");
            }

            public void messageArrived(String s, MqttMessage mqttMessage) throws Exception {
                System.out.println("<<< Subscribe from IoT server. topic : " + s + ", message : " + mqttMessage.toString());
            }

            public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
                System.out.println(">>> Publish to IoT server.");
            }
        });

        /*
        Topic & Message Example
        */
        String sendTopic = "factory/room1/temperature";

        // Test for MQTT republish
        // In order to receive alert topic message, alert republish action must be set in Rule engine.
        String alertTopic = "alert";

        // Console guide example message
        String message = "{ \"deviceId\": \"device_1\", \"deviceType\": \"temperature\", \"value\": 35, \"battery\": 9, \"date\": \"2016-12-15\", \"time\": \"15:12:00\"}";


        /*
        Subscribe message
         */
        boolean isConnected = mqttClient.isConnected();
        if (isConnected) {
            mqttClient.subscribe(alertTopic);

            // You can check whether the message is being delivered normally.
//            mqttClient.subscribe(sendTopic);
        }

        /*
        Publish message
         */
        if (isConnected) {
            for (int i=0; i < 5; i++) {
                MqttMessage mqttMessage = new MqttMessage(message.getBytes());
                mqttMessage.setQos(0);
                mqttMessage.setRetained(false);

                try {
                    MqttTopic topic = mqttClient.getTopic(sendTopic);
                    MqttDeliveryToken token = topic.publish(mqttMessage);
                    token.waitForCompletion();
                    Thread.sleep(2000);

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }

        /*
        Enable disconnect() and close() if you needed
         */
//        mqttClient.disconnect();
//        mqttClient.close();
    }


    /*
    Code for Certificate Access
     */

    private MqttExample() {
        init();
    }

    private KeyManagerFactory getKeyManagerFactory(String clientCaChainFilePath, String clientCertFilePath, String clientKeyFilePath, String password) throws KeyStoreException, IOException, NoSuchAlgorithmException, CertificateException, UnrecoverableKeyException {

        // load client private key
        KeyPair key = getClientKey(clientKeyFilePath);

        // load client Cert
        Certificate clientCert = getClientCert(clientCertFilePath);

        // load client CA Chain
        List<Certificate> caChain = getClientCaChain(clientCaChainFilePath, clientCert);

        KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
        ks.load(null, null);
        int caChainSize = caChain.size();
        Certificate[] caChainArray = caChain.toArray(new Certificate[caChainSize]);
        ks.setKeyEntry("private-key", key.getPrivate(), password.toCharArray(), caChainArray);
        KeyManagerFactory kmf = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
        kmf.init(ks, password.toCharArray());

        return kmf;
    }

    private TrustManagerFactory getTrustManagerFactory(String rootCaCertFilePath) throws KeyStoreException, IOException, NoSuchAlgorithmException, CertificateException {
        // load CA certificate
        X509Certificate rootCaCert = getRootCaCert(rootCaCertFilePath);

        KeyStore rootCaKeyStore = KeyStore.getInstance(KeyStore.getDefaultType());
        rootCaKeyStore.load(null, null);
        rootCaKeyStore.setCertificateEntry("ca-certificate", rootCaCert);
        TrustManagerFactory tmf = TrustManagerFactory.getInstance("X509");
        tmf.init(rootCaKeyStore);

        return tmf;
    }


    private void init() {
        Security.addProvider(new BouncyCastleProvider());
    }

    private KeyPair getClientKey(String clientKeyFilePath) throws IOException {
        PEMParser pemParser = new PEMParser(new FileReader(clientKeyFilePath));
        Object object = pemParser.readObject();
        JcaPEMKeyConverter converter = new JcaPEMKeyConverter().setProvider("BC");

        KeyPair key = converter.getKeyPair((PEMKeyPair) object);
        pemParser.close();
        return key;
    }

    private List<Certificate> getClientCaChain(String clientCaChainFilePath, Certificate clientCert) throws CertificateException, IOException {
        X509Certificate cert;
        List<Certificate> caChain = new ArrayList<Certificate>();

        BufferedInputStream bis = new BufferedInputStream(new FileInputStream(clientCaChainFilePath));
        CertificateFactory cf = CertificateFactory.getInstance("X.509");

        while (bis.available() > 0) {
            cert = (X509Certificate) cf.generateCertificate(bis);
            caChain.add(cert);
        }

        caChain.add(0, clientCert);
        return caChain;
    }

    private X509Certificate getClientCert(String clientCertFilePath) throws CertificateException, IOException {
        return getX509Certificate(clientCertFilePath);
    }

    private X509Certificate getRootCaCert(String rootCaCertFilePath) throws CertificateException, IOException {
        return getX509Certificate(rootCaCertFilePath);
    }

    private X509Certificate getX509Certificate(String rootCaCertFilePath) throws CertificateException, IOException {
        X509Certificate caCert = null;

        BufferedInputStream bis = new BufferedInputStream(new FileInputStream(rootCaCertFilePath));
        CertificateFactory cf = CertificateFactory.getInstance("X.509");

        while (bis.available() > 0) {
            caCert = (X509Certificate) cf.generateCertificate(bis);
        }
        return caCert;
    }
}

          Execution result

          The following is the execution result of the Java example code.

          === Successfully Connected
>>> Publish to IoT server.
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert, message : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert, message : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}
<<< Subscribe from IoT server. topic : alert, message : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert, message : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert, message : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}

          Python

          An example code to access Cloud IoT Core, repeat publish and subscribe messages 5 times, and end the program. The messages are published on the factory/room1/temperature topic, and the alert topic, which is republished through Cloud IoT core, is subscribed.

          Settings

          To run the example file, the paho-mqtt library must be installed.

          pip install paho-mqtt //python 2.x
python -m pip install paho-mqtt // python 2.7.9+
python3 -m pip install paho-mqtt //python 3.x
          Note

          The full certificate chain value in the example file refers to the path where the full certificate chain file will be saved, connecting certificates with a chain certificate. When you run this Python code, the full certificate chain file is automatically saved in the specified path.

          Example code

          • mqttTLSClient.py

            # coding=utf-8
import argparse
import logging
import paho.mqtt.client as mqttClient
import ssl
import time
import json

def main():
    # init
    initLogger()
    initParameter()
    appendCert()

    # Connect MQTT Broker
    client = mqttClient.Client()
    if not connectTls(client, hostname, port, rootCa, fullCertChain, private):
        client.loop_stop()
        exit(1)

    attempts = 0
    while attempts < 5:
        # Subscribe message
        client.subscribe("alert",0)
        # Publish Message to Message broker
        publish(client, topic, payload)
        time.sleep(publishDelay)
        attempts += 1

    time.sleep(5)

def initLogger():
    global log
    log = logging.getLogger(__name__)
    log.setLevel(logging.ERROR)

    # stream handler (print to console)
    streamHandler = logging.StreamHandler()

    # file formatter
    formatter = logging.Formatter('[%(asctime)s] [%(levelname)s] (%(filename)s:%(funcName)s:%(lineno)d) : %(message)s')
    streamHandler.setFormatter(formatter)

    log.addHandler(streamHandler)

def initParameter():
    global rootCa
    global caChain
    global cert
    global private
    global fullCertChain

    global hostname
    global port
    global publishDelay

    global topic
    global payload

    global connected

    rootCa = '/<Your>/<file>/<path>/rootCaCert.pem'
    caChain = '/<Your>/<file>/<path>/caChain.pem'
    cert = '/<Your>/<file>/<path>/cert.pem'
    private = '/<Your>/<file>/<path>/private.pem'

    hostname = 'msg01.cloudiot.ntruss.com'
    port = 8883
    publishDelay = 1 # sec

    topic = "factory/room1/temperature"
    payload = "{ \"deviceId\": \"device_1\", \"deviceType\": \"temperature\", \"value\": 35, \"battery\": 9, \"date\": \"2016-12-15\", \"time\": \"15:12:00\"}"

    connected = False

    #fullCertChain is automatically generated by cert and caChain
    fullCertChain = './fullCertChain.pem'


def appendCert():
    filenames = [cert, caChain]
    with open(fullCertChain,'w') as outfile:
         for fname in filenames :
            with open(fname) as infile:
                outfile.write(infile.read()+"\n")

def connectTls(client, hostname, port, rootCa, fullCertChain, clientKey):
    client.on_connect = on_connect
    client.on_message = on_message
    client.on_publish = on_publish

    client.tls_set(ca_certs=rootCa, certfile=fullCertChain,
                   keyfile=clientKey, cert_reqs=ssl.CERT_REQUIRED,
                  tls_version=ssl.PROTOCOL_TLSv1_2, ciphers=None)

    ssl.match_hostname = lambda cert, hostname: True
    client.tls_insecure_set(False)
    client.connect(hostname, port=port)
    client.loop_start()

    attempts = 0

    while not connected and attempts < 5:  # Wait for connection
        time.sleep(1)
        attempts += 1

    if not connected:
        return False

    return True

def on_connect(client, userdata, flags, rc):
    if rc == 0:
        log.info("=== Successfully Connected")
        global connected  # Use global variable
        connected = True  # Signal connection
    else:
        log.error("=== Connection lost")

def on_publish(client, userdata, result):
     print(">>> Publish to IoT server.")

def publish(client, topic, payload):
    try:
        client.publish(topic, payload)
    except Exception as e:
        print("[ERROR] Could not publish data, error: {}".format(e))

def on_message(client, userdata, message):
    print("<<< Subscribe from IoT server. topic : "+ message.topic + ", message : " + str(message.payload.decode("utf-8")))


if __name__ == "__main__":
    main()

          Execution result

          The following is the execution result of mqttTLSClient.py.

          >>> Publish to IoT server.
>>> Publish to IoT server.
>>> Publish to IoT server.
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert, message : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}
<<< Subscribe from IoT server. topic : alert, message : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}
<<< Subscribe from IoT server. topic : alert, message : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert, message : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}
<<< Subscribe from IoT server. topic : alert, message : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}

          Node JS(JavaScript)

          An example code to access Cloud IoT Core, repeat publish and subscribe messages 5 times, and end the program. The messages are published on the factory/room1/temperature topic, and the alert topic, which is republished through Cloud IoT core, is subscribed.

          Settings

          The Node JS (JavaScript) example needs the mqtt library to be installed, and before installing the library, the node package manager (npm) must be installed. Place package.json and MqttClient.js files in the same folder, and then use npm install command to download and run the node library package.

          • package.json
          {
  "name": "cloud-iot-mqtt-sample",
  "version": "0.1.0",
  "dependencies": { "mqtt": "^1.14.1" }
}

          Example code

          • MqttClient.js
            const mqtt = require('mqtt');
const fs = require('fs');
const path = require('path');

const HOST = "msg01.cloudiot.ntruss.com";
const PORT = 8883;
const PUBLISH_TOPIC = `factory/room1/temperature`;
const SUBSCRIBE_TOPIC = `alert`;
const QOS = 0;

const certFolderPath = "/<Your>/<file>/<path>/";
const KEY = fs.readFileSync(certFolderPath + `private.pem`);
const CERT = fs.readFileSync(certFolderPath + `cert.pem`);
const CA_CHAIN = fs.readFileSync(certFolderPath + `caChain.pem`);
const TRUSTED_CA_LIST = fs.readFileSync(certFolderPath + `rootCaCert.pem`);
const FULL_CERTIFICATION = CERT+"\n"+CA_CHAIN;

let receivedIndex = 0;

const connectionInfo = {
  port: PORT,
  host: HOST,
  key: KEY,
  cert: FULL_CERTIFICATION,
  ca: TRUSTED_CA_LIST,
  rejectUnauthorized: true,
  protocol: 'mqtts',
  connectTimeout: 60 * 1000,
  keepalive: 1000,
}

const client = mqtt.connect(connectionInfo);

// Connetion to mqtt message broker //
client.on('connect', async function () {
  console.log('=== Successfully Connected');

  for (let i = 0; i < 5; i++) {
    await sleep(1000);
    sendMessage();
  }
})

// Subscribe to Message //
function sendMessage() {
  console.log(">>> Publish to IoT server.")
  client.publish(PUBLISH_TOPIC, getMsg())
}

// Subscribe to Message //
client.subscribe(SUBSCRIBE_TOPIC, {qos:QOS});

// Receiving Message //
client.on('message', async function (topic, message) {
  console.log(`<<< Subscribe from IoT server. topic : "${topic}", message(${receivedIndex}) : ${message.toString()}`);
  receivedIndex++;

  if (receivedIndex == 5) {
    client.end();
    console.log("=== Complete.")
  }
})

client.on('close', function () {
  console.log("connection Close");
})

client.on('error', function (err) {
  console.log(err.toString());
})

function getMsg () {
  const timeStamp = Math.floor(new Date() / 1000);
  const msg = `{"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}`;
  return msg;
}

const sleep = (ms) => {
     return new Promise(resolve=>{
         setTimeout(resolve,ms);
     })
 }

          Execution result

          The following is the execution result of the Node JS (JavaScript) example code.

          === Successfully Connected
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : "factory/room1/temperature", message(0) : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : "factory/room1/temperature", message(1) : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : "factory/room1/temperature", message(2) : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : "factory/room1/temperature", message(3) : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : "factory/room1/temperature", message(4) : {"battery":9,"date":"2016-12-15","deviceId":"device_1","deviceType":"temperature","time":"15:12:00","value":35}
=== Complete.
connection Close

          C

          An example code to access Cloud IoT Core, repeat publish and subscribe messages 5 times, and end the program. The messages are published on the factory/room1/temperature topic, and the alert topic, which is republished through Cloud IoT core, is subscribed.

          Settings

          To run this example file, you need to install the Paho MQTT library.

          • CentOS

            $ sudo yum install build-essential gcc make cmake cmake-gui cmake-curses-gui
$ sudo yum install openssl-devel
$ git clone https://github.com/eclipse/paho.mqtt.c
$ cd paho.mqtt.c
$ git checkout v1.3.8
$ make
$ sudo make install

          • Ubuntu

            $ sudo apt-get install build-essential gcc make cmake cmake-gui cmake-curses-gui
$ sudo apt-get install libssl-dev
$ git clone https://github.com/eclipse/paho.mqtt.c.git
$ cd paho.mqtt.c
$ git checkout v1.3.8
$ cmake -Bbuild -H. -DPAHO_ENABLE_TESTING=OFF -DPAHO_BUILD_STATIC=ON \
    -DPAHO_WITH_SSL=ON -DPAHO_HIGH_PERFORMANCE=ON
$ sudo cmake --build build/ --target install
$ sudo ldconfig
          Note

          The full certificate chain path value in the example file refers to the path where the full certificate chain file will be saved, connecting certificates with a chain certificate. When you run the example, the full certificate chain file is automatically saved in the path you set.

          Example code

          • mqttClient.c

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

#include "MQTTClient.h"

#define QOS 1
#define TIMEOUT 10000L

volatile MQTTClient_deliveryToken deliveredtoken;

// Generate fullCertChain by cert and caChain
void appendCert(char* cert, char* caChain, char* fullCertChain) {

    FILE* fpw = fopen(fullCertChain,"w");
    FILE* fpr = fopen(cert,"r");
    int size;
    char* buffer;

    fseek(fpr, 0, SEEK_END);
    size = ftell(fpr);
    buffer = (char*)malloc(size + 1);
    memset(buffer, 0, size + 1);
    fseek(fpr, 0, SEEK_SET);
    fread(buffer, size, 1, fpr);

    fputs(buffer, fpw);
    fclose(fpr);
    free(buffer);
    fputs("\n", fpw);

    fpr = fopen(caChain,"r");
    fseek(fpr, 0, SEEK_END);
    size = ftell(fpr);
    buffer = (char*)malloc(size + 1);
    memset(buffer, 0, size + 1);
    fseek(fpr, 0, SEEK_SET);
    fread(buffer, size, 1, fpr);

    fputs(buffer, fpw);
    fputs("\n", fpw);

    free(buffer);
    fclose(fpr);
    fclose(fpw);
}

void delivered( void *context, MQTTClient_deliveryToken dt )
{
    printf(">>> Publish to IoT server.\n");
    deliveredtoken = dt;
}

int msgarrvd(void *context, char *topicName, int topicLen, MQTTClient_message *message) {
    char* payload = (char*)message->payload;
    printf("<<< Subscribe from IoT server. topic : %s , message : %s\n", topicName, payload);
    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[])
{

    char clientId[] = "myClientTest";

    // Modify file path and server
    // MQTT server hostname
    char iotServer[] = "ssl://msg01.cloudiot.ntruss.com:8883";


    char rootCaCertFilePath[] = "/<Your>/<file>/<path>/rootCaCert.pem";
    char clientCaChainFilePath[] = "/<Your>/<file>/<path>/caChain.pem";
    char clientCertFilePath[] = "/<Your>/<file>/<path>/cert.pem";
    char clientKeyFilePath[] = "/<Your>/<file>/<path>/private.pem";

    // fullCertChain is automatically generated by cert and caChain
    char fullCertChainPath[] = "./fullCertChain.pem";
    char password[] = "";


    // Topic & Message Example
    char sendTopic[] = "factory/room1/temperature";
    char alertTopic[] = "alert";
    char payload[] = "{ \"deviceId\": \"device_1\", \"deviceType\": \"temperature\", \"value\": 35, \"battery\": 9, \"date\": \"2016-12-15\", \"time\": \"15:12:00\"}";


    MQTTClient client;
    MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
    MQTTClient_SSLOptions ssl_opts = MQTTClient_SSLOptions_initializer;
    MQTTClient_message pubmsg = MQTTClient_message_initializer;
    MQTTClient_deliveryToken token;
    int rc;
    int setCallBack;
    int attempts;

    MQTTClient_create(&client, iotServer, clientId, MQTTCLIENT_PERSISTENCE_NONE, NULL);

    // Generate fullCertChain by cert and caChain
    appendCert(clientCertFilePath, clientCaChainFilePath, fullCertChainPath);

    // MQTT Connection parameters
    ssl_opts.verify = 1;
    ssl_opts.trustStore = rootCaCertFilePath;
    ssl_opts.keyStore = fullCertChainPath;
    ssl_opts.privateKey = clientKeyFilePath;

    conn_opts.ssl = &ssl_opts;

    conn_opts.keepAliveInterval = 20;
    conn_opts.cleansession = 1;
    conn_opts.serverURIcount = 0;
    conn_opts.serverURIs = NULL;

    // Set call back
    if((setCallBack = MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd, delivered)) != MQTTCLIENT_SUCCESS)
    {
        printf("ERROR : MQTTClient_setCallbacks, setCallBack = %d\n", setCallBack);
        return setCallBack;
    }


    // Connect MQTT Broker
    if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
    {
        printf("ERROR : Failed to connect, return code : %d\n", rc);
        exit(-1);
    } 


    // Subscribe message
    rc = MQTTClient_subscribe(client, alertTopic, 0);

    pubmsg.payload = payload;
    pubmsg.payloadlen = strlen(payload);
    pubmsg.qos = QOS;
    pubmsg.retained = 0;

    for(attempts=0; attempts<5; attempts++){
        // Publish message
        MQTTClient_publishMessage(client, sendTopic, &pubmsg, &token);
        rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);

        sleep(2);       //sec
    }

    sleep(2);           //sec

    // Disconnect
    MQTTClient_disconnect(client, 10000);
    MQTTClient_destroy(&client);

    return rc;
}

          Run example code

          The following shows how to run the C example code.

          $ gcc -o {executable file name} {source file name}.c -l paho-mqtt3cs
$ ./{executable file name}

          Execution result

          The following is the execution result of the C example code.

          >>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert , message : {"deviceType":"temperature","date":"2016-12-15","time":"15:12:00","battery":9,"deviceId":"device_1","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert , message : {"deviceType":"temperature","date":"2016-12-15","time":"15:12:00","battery":9,"deviceId":"device_1","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert , message : {"deviceType":"temperature","date":"2016-12-15","time":"15:12:00","battery":9,"deviceId":"device_1","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert , message : {"deviceType":"temperature","date":"2016-12-15","time":"15:12:00","battery":9,"deviceId":"device_1","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert , message : {"deviceType":"temperature","date":"2016-12-15","time":"15:12:00","battery":9,"deviceId":"device_1","value":35}

          C++

          An example code to access Cloud IoT Core, repeat publish and subscribe messages 5 times, and end the program. The messages are published on the factory/room1/temperature topic, and the alert topic, which is republished through Cloud IoT core, is subscribed.

          Settings

          To run this example file, you need to install the Paho MQTT library.

          • CentOS

            $ sudo yum install build-essential gcc make cmake cmake-gui cmake-curses-gui
$ sudo yum install openssl-devel
$ git clone https://github.com/eclipse/paho.mqtt.c
$ cd paho.mqtt.c
$ git checkout v1.3.8
$ make
$ sudo make install

          • Ubuntu

            $ sudo apt-get install build-essential gcc make cmake cmake-gui cmake-curses-gui
$ sudo apt-get install libssl-dev
$ git clone https://github.com/eclipse/paho.mqtt.c.git
$ cd paho.mqtt.c
$ git checkout v1.3.8
$ cmake -Bbuild -H. -DPAHO_ENABLE_TESTING=OFF -DPAHO_BUILD_STATIC=ON \
    -DPAHO_WITH_SSL=ON -DPAHO_HIGH_PERFORMANCE=ON
$ sudo cmake --build build/ --target install
$ sudo ldconfig
          Note

          The full certificate chain path value in the example file refers to the path where the full certificate chain file will be saved, connecting certificates with a chain certificate. When you run the example, the full certificate chain file is automatically saved in the path you set.

          Example code

          • mqttClient.cpp
            #include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <iostream>
#include <fstream>

#include "MQTTClient.h"

#define QOS 1
#define TIMEOUT 10000L

volatile MQTTClient_deliveryToken deliveredtoken;

// Generate fullCertChain by cert and caChain
void appendCert(char* cert, char* caChain, char* fullCertChain) {

    std::ifstream fin;
    std::ofstream fout;
    int size;
    char* buffer;

    fin.open(cert);
    fout.open(fullCertChain);

    fin.seekg(0,std::ios::end);
    size = fin.tellg();
    fin.seekg(0, std::ios::beg);

    buffer = (char*)malloc(size + 1);
    memset(buffer, 0, size + 1);
    fin.read(&buffer[0], size);

    fout << buffer << std::endl;
    free(buffer);
    fin.close();

    fin.open(caChain);
    fin.seekg(0,std::ios::end);
    size = fin.tellg();
    fin.seekg(0, std::ios::beg);
    buffer = (char*)malloc(size + 1);
    memset(buffer, 0, size + 1);
    fin.read(&buffer[0], size);

    fout << buffer << std::endl;
    free(buffer);
    fin.close();
    fout.close();
}

void delivered( void *context, MQTTClient_deliveryToken dt )
{
    std::cout << ">>> Publish to IoT server." << std::endl;
    deliveredtoken = dt;
}

int msgarrvd(void *context, char *topicName, int topicLen, MQTTClient_message *message) {
    char* payload = (char*)message->payload;
    std::cout << "<<< Subscribe from IoT server. topic : " << topicName << " , message : " << payload << std::endl;
    MQTTClient_freeMessage(&message);
    MQTTClient_free(topicName);
    return 1;
}

void connlost( void *context, char *cause )
{
    std::cout << std::endl << "Connection lost" << std::endl;
    std::cout << "     cause: " << cause << std::endl;
}

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

    char clientId[] = "myClientTest";

    // Modify file path and server
    // MQTT server hostname
    char iotServer[] = "ssl://msg01.cloudiot.ntruss.com:8883";

    char rootCaCertFilePath[] = "/<Your>/<file>/<path>/rootCaCert.pem";
    char clientCaChainFilePath[] = "/<Your>/<file>/<path>/caChain.pem";
    char clientCertFilePath[] = "/<Your>/<file>/<path>/cert.pem";
    char clientKeyFilePath[] = "/<Your>/<file>/<path>/private.pem";

    // fullCertChain is automatically generated by cert and caChain
    char fullCertChainPath[] = "./fullCertChain.pem";
    char password[] = "";


    // Topic & Message Example
    char sendTopic[] = "factory/room1/temperature";
    char alertTopic[] = "alert";
    char payload[] = "{ \"deviceId\": \"device_1\", \"deviceType\": \"temperature\", \"value\": 35, \"battery\": 9, \"date\": \"2016-12-15\", \"time\": \"15:12:00\"}";


    MQTTClient client;
    MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
    MQTTClient_SSLOptions ssl_opts = MQTTClient_SSLOptions_initializer;
    MQTTClient_message pubmsg = MQTTClient_message_initializer;
    MQTTClient_deliveryToken token;
    int rc;
    int setCallBack;
    int attempts;

    MQTTClient_create(&client, iotServer, clientId, MQTTCLIENT_PERSISTENCE_NONE, NULL);

    // Generate fullCertChain by cert and caChain
    appendCert(clientCertFilePath, clientCaChainFilePath, fullCertChainPath);

    // MQTT Connection parameters
    ssl_opts.verify = 1;
    ssl_opts.trustStore = rootCaCertFilePath;
    ssl_opts.keyStore = fullCertChainPath;
    ssl_opts.privateKey = clientKeyFilePath;

    conn_opts.ssl = &ssl_opts;

    conn_opts.keepAliveInterval = 20;
    conn_opts.cleansession = 1;
    conn_opts.serverURIcount = 0;
    conn_opts.serverURIs = NULL;

    // Set call back
    if((setCallBack = MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd, delivered)) != MQTTCLIENT_SUCCESS)
    {
        std::cout << "ERROR : MQTTClient_setCallbacks, setCallBack = " << setCallBack << std::endl;
        return setCallBack;
    }


    // Connect MQTT Broker
    if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
    {
        std::cout << "ERROR : Failed to connect, return code : " << rc << std::endl;
        exit(-1);
    } 


    // Subscribe message
    rc = MQTTClient_subscribe(client, alertTopic, 0);

    pubmsg.payload = payload;
    pubmsg.payloadlen = strlen(payload);
    pubmsg.qos = QOS;
    pubmsg.retained = 0;

    for(attempts=0; attempts<5; attempts++){
        // Publish message
        MQTTClient_publishMessage(client, sendTopic, &pubmsg, &token);
        rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);

        sleep(2);       //sec
    }

    sleep(2);           //sec

    // Disconnect
    MQTTClient_disconnect(client, 10000);
    MQTTClient_destroy(&client);

    return rc;
}

          Run example code

          The following shows how to run the C ++ example code.

          $ g++ -o {executable file name} {source file name}.cpp -l paho-mqtt3cs
$ ./{executable file name}

          Execution result

          The following is the creation result of the C++ example code.

          >>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert , message : {"deviceType":"temperature","date":"2016-12-15","time":"15:12:00","battery":9,"deviceId":"device_1","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert , message : {"deviceType":"temperature","date":"2016-12-15","time":"15:12:00","battery":9,"deviceId":"device_1","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert , message : {"deviceType":"temperature","date":"2016-12-15","time":"15:12:00","battery":9,"deviceId":"device_1","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert , message : {"deviceType":"temperature","date":"2016-12-15","time":"15:12:00","battery":9,"deviceId":"device_1","value":35}
>>> Publish to IoT server.
<<< Subscribe from IoT server. topic : alert , message : {"deviceType":"temperature","date":"2016-12-15","time":"15:12:00","battery":9,"deviceId":"device_1","value":35}
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