driver: 7bee5263

mqtt: 6c098065

nopoll: 31f0ea07

ssl: eefb383a

This MQTT demo is based on the Eclipse Paho MQTT library, and demonstrates a working MQTT client actions(subscribe, publish, ping). Using this MQTT demo, you can connect to the MQTT broker, subscribe to a topic and publish messages to the predefined topic.

Also, this demo will ping the MQTT broker in the defined interval if no sending or receiving action happens. And we add some APIs to realize the SSL functionality, these SSL APIs provide the one-way certification and two-way certification.

Some basic configurations need to be done before starting this demo and are listed in the include/user_config.h.

* Wi-Fi SSID & Password

* MQTT Broker Address(can be a domain name) & MQTT Port

This section describes the mqtt informations and API for MQTT client without SSL functionality.

For this MQTT demo, mqtt-related informations are defined in the mqtt_client_thread(), and they are listed below.

* two buffers(i.e. sendbuf[80] & readbuf[80]) to store packets to be sent and received

* MQTTVersion, ClientID, KeepAliveInterval, etc are defined using **MQTTPacket_connectData_initializer**

* Command_timeout is defined as 30s, and you can use this value as default

* The subscribe topic is defined as "ESP8266/sample/sub"

* The subscribe message handler is "void messageArrived(MessageData* data)"

* The publish topic is defined as "ESP8266/sample/pub"

* The published message's QoS type is QoS2

These informarions are only defined as a demonstration, you can change them appropriately according to your own requirements.

1.Platform-Related

* NetworkInit(): used to initialize **Network** structure, which includes read/write functions, etc.

* NetworkConnect(): used to create socket and connect to the MQTT broker

2.MQTT-Related

* MQTTClientInit(): used to initialize **MQTTClient** structure, which includes MQTT client information

* MQTTStartTask(): a task used to perform MQTT **keep alive**

* MQTTConnect(): used to perform MQTT connect

* MQTTSubscribe(): used to subscribe to a topic

* MQTTPublish(): used to publish messages to a topic

This section describes the mqtt informations and API for MQTT client with SSL functionality enabled.

The aforementioned informations in the **MQTT Info** section of **MQTT-Normal** are also used for MQTT-SSL. As for SSL functionality, some more information will be needed and are listed below in the "Added-Info" section.

1.Existed-Info

This section is the same with the **MQTT Info** section of **MQTT-Normal**.

2.Added-Info

* May need header files of CA (and client certificate & key) included in the include/ directory

* May need length of the CA (and client certificate & key) files

* Need a **ssl_ca_crt_key_t** structure initialized using the CA (and client certificate & key) files

When SSL is enabled, the Platform-related API are different with **MQTT-Normal** section.

1.Platform-related

* NetworkInitSSL(): used to initialize **Network** structure, which includes SSL read/write functions, etc.

* NetworkConnectSSL(): used to create socket and connect to the MQTT broker with SSL enabled

2.MQTT-Related

This section is the same with the "MQTT-Related" section of "MQTT-Normal".

For SSL functionality, three certification ways may be used: no certification, one-way certification and two-way certification. The specific configurations for each of them are described below:

1.No Certification

* No CA file and client certificate & key files need to be included

* Define a **ssl_ca_crt_key_t** structure

* Set the **cacrt**, **cert** and **key** parameters within the structure to be **NULL**

* Recommend to set the **verify_mode** parameter to **SSL_VERIFY_NONE**

* Set the **method** parameter to **TLSv1_1_client_method()** or **TLSv1_2_client_method()**

* Set the **frag_len** parameter with a value between **2048** and **8192**

2.One-way Certification

* CA file shall be included, also length of the CA file shall be provided

* Define a **ssl_ca_crt_key_t** structure

* Set the **cacrt** parameter within the structure to the array in the CA file

* Set the **cacrt_len** parameter to length of the CA file

* Set the **verify_mode** parameter to **SSL_VERIFY_PEER**

* Set the **method** parameter to **TLSv1_1_client_method()** or **TLSv1_2_client_method()**

* Set the **frag_len** parameter with a value between **2048** and **8192**

3.Two-way Certification

* CA file and client certificate & key files shall be included

* Also length of the CA file and client certificate & key files shall be provided

* Define a **ssl_ca_crt_key_t** structure

* Set the **cacrt** parameter within the structure to the array in the CA file

* Set the **cacrt_len** parameter to length of the CA file

* Set the **cert** parameter within the structure to the array in the client certificate file

* Set the **cert_len** parameter to length of the client certificate file

* Set the **key** parameter within the structure to the array in the client key file

* Set the **key_len** parameter to length of the client key file

* Set the **verify_mode** parameter to **SSL_VERIFY_PEER**

* Set the **method** parameter to **TLSv1_1_client_method()** or **TLSv1_2_client_method()**

* Set the **frag_len** parameter with a value between **2048** and **8192**

The following shows a simple demo of the MQTT client SSL functionality, and only the different places compared with MQTT-Normal demo are displayed. The names of CA file, client certificate & key files are just a demonstration, changing these properly according to your own files.

#include "openssl/ssl.h"

#include "CA.h"

#include "cert.h"

#include "key.h"

ssl_ca_crt_key_t ssl_cck;

#define SSL_CA_CERT_KEY_INIT(s,a,b,c,d,e,f) ((ssl_ca_crt_key_t *)s)->cacrt = a;\

((ssl_ca_crt_key_t *)s)->cacrt_len = b;\

((ssl_ca_crt_key_t *)s)->cert = c;\

((ssl_ca_crt_key_t *)s)->cert_len = d;\

((ssl_ca_crt_key_t *)s)->key = e;\

((ssl_ca_crt_key_t *)s)->key_len = f;

static void mqtt_client_thread(void *pvParameters)

{

......

NetworkInitSSL(&network);

......

SSL_CA_CERT_KEY_INIT(&ssl_cck, ca_crt, ca_crt_len, client_crt, client_crt_len, client_key, client_key_len);

if ((rc = NetworkConnectSSL(&network, address, MQTT_PORT, &ssl_cck, TLSv1_1_client_method(), SSL_VERIFY_NONE, 8192)) != 1) {

printf("Return code from network connect ssl is %d\n", rc);

}

......

}

#define SSID "espressif" /* Wi-Fi SSID */

#define PASSWORD "1234567890" /* Wi-Fi Password */

#define MQTT_BROKER "iot.eclipse.org" /* MQTT Broker Address*/

#define MQTT_PORT 1883 /* MQTT Port*/