Demo 30: How to use Arduino ESP32 MQTTS with MQTTS Mosquitto broker (TLS/SSL)

1. Introduction
Arduino-ESP32 SDK has been updated and new WiFiClientSecure library not working any more. In order to fix it, please using the old github commit or download the zip file here.
After downloading the old commit; extract it; go to the libraries folder; copy the
WiFiClientSecure folder; replace the current WiFiClientSecure folder (in Arduino/hardware/espressif/esp32/libraries or refer here) by the copied WiFiClientSecure folder.
- In this tutorial, I will show you how to use ESP32 MQTTS with MQTTS Mosquitto broker (TLS/SSL).
- In order to make this tutorial, please refer topics:
How to set up secure transportation for MQTT Mosquitto broker with SSL/TLS
Demo 29: How to use HTTPS in Arduino ESP32
Demo 14: How to use MQTT and Arduino ESP32 to build a simple Smart home system
- The requirement for this demo: ESP32 with a LED on it will turn On/Off when subscribing a topic "smarthome/room1/led" with values (0: off, 1: on).
2. Steps
- After doing the steps in this demo How to set up secure transportation for MQTT Mosquitto broker with SSL/TLS, you have to extract the content of ca.crt for SSL/TLS handshake phase by running the command:  
cat /etc/mosquitto/certs/ca.crt

 Figure: Extract content of ca.crt

- Get the IP address of machine that run MQTT mosquitto by running command: ifconfig or if you use MDNS for that machine you can follow this tutorial to get the IP directly from ESP32: How to get the IP address of a node by its mdns host name in Arduino ESP32.

- We will use WiFiClientSecure class for SSL/TLS handshake phase and PubSubClient library for ESP32 MQTT communication. Please see the topics that I mentioned above.

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#include <WiFi.h> #include <WiFiClientSecure.h> #include <PubSubClient.h> #include <ESPmDNS.h> /* change it with your ssid-password */ const char* ssid = "dd-wrt"; const char* password = "0000000000"; /* this is the MDNS name of PC where you installed MQTT Server */ const char* serverHostname = "iotsharing"; const char* ca_cert = \ "-----BEGIN CERTIFICATE-----\n" \ "MIIDpzCCAo+gAwIBAgIJAOHc50EeJ6aeMA0GCSqGSIb3DQEBDQUAMGoxFzAVBgNV\n" \ "BAMMDkFuIE1RVFQgYnJva2VyMRYwFAYDVQQKDA1Pd25UcmFja3Mub3JnMRQwEgYD\n" \ "VQQLDAtnZW5lcmF0ZS1DQTEhMB8GCSqGSIb3DQEJARYSbm9ib2R5QGV4YW1wbGUu\n" \ "bmV0MB4XDTE3MDgyNzAyMDQwNFoXDTMyMDgyMzAyMDQwNFowajEXMBUGA1UEAwwO\n" \ "QW4gTVFUVCBicm9rZXIxFjAUBgNVBAoMDU93blRyYWNrcy5vcmcxFDASBgNVBAsM\n" \ "C2dlbmVyYXRlLUNBMSEwHwYJKoZIhvcNAQkBFhJub2JvZHlAZXhhbXBsZS5uZXQw\n" \ "ggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQC8mQfR058k7LBV7Xt6RiZL\n" \ "BIpC5ewSweAnsaS6Ue+jx6uruJsccnIJbiHJVjOcSYV3JLMt3un7d0JTottW6Zx/\n" \ "VleYC4CUzf3bcHLe7Qhl0veP9QAdZceblMCbEqAM9227EaXKQVzAYGwRnuxvfJM7\n" \ "P84iu2J/zB4o+AEWUJDIW38SO4b+0i1FYHmKKxEx7dztDyCJvTsn35wX3oKlJ5e+\n" \ "na/6csD+Ngh9QQ+wDd02TBqXKB7UXyRT5ECesu19U6CTE7Wr9xECbDO262aD6GtC\n" \ "HpeSAWqa6HKbKjZ20pL5V5ceS85TdWbvPdVrFUDWMIhK9dNuwhIK0s6VyRcJkbe5\n" \ "AgMBAAGjUDBOMB0GA1UdDgQWBBQPZ0u1jIg65jT3Th42VGMnya6VDDAfBgNVHSME\n" \ "GDAWgBQPZ0u1jIg65jT3Th42VGMnya6VDDAMBgNVHRMEBTADAQH/MA0GCSqGSIb3\n" \ "DQEBDQUAA4IBAQB8JrNsV32aXBOLSX8WqoHuU2NOJH+1fTdGDLYLEAPe/x3YxkNC\n" \ "MJDx8TGLSQsz4L0kCsLEQ/qsnkuPJUt3x7eNIMOrvS+zDv9wXqnGwMgeAOtEkG5n\n" \ "NbPezM50ovgZAuEZMphp2s/Zl0EROydnqpkweWa5bxYRkiQBlp0nUkCtec3PZ6iO\n" \ "QVPj/bHHi4T3jkbL0+oLNShv9Zw9hr6BkKCVqeHe9prlOMVuEJOVrEKzkhhAY90p\n" \ "Wwrj+OQYCLllJVD9VQhLVOXLg1bSuqkld3PCQBFNvrvk4Up61wuu/Oj5c5g8vwYd\n" \ "0ul29sU3heTw4ZXifpbMXRM36LFNH5uLrSba\n" \ "-----END CERTIFICATE-----\n"; /* create an instance of WiFiClientSecure */ WiFiClientSecure espClient; PubSubClient client(espClient); /*LED GPIO pin*/ const char led = 4; /* topics */ #define COUNTER_TOPIC "smarthome/room1/counter" #define LED_TOPIC "smarthome/room1/led" /* 1=on, 0=off */ long lastMsg = 0; char msg[20]; int counter = 0; void receivedCallback(char* topic, byte* payload, unsigned int length) { Serial.print("Message received: "); Serial.println(topic); Serial.print("payload: "); for (int i = 0; i < length; i++) { Serial.print((char)payload[i]); } Serial.println(); /* we got '1' -> on */ if ((char)payload[0] == '1') { digitalWrite(led, HIGH); } else { /* we got '0' -> on */ digitalWrite(led, LOW); } } void mqttconnect() { /* Loop until reconnected */ while (!client.connected()) { Serial.print("MQTT connecting ..."); /* client ID */ String clientId = "ESP32Client"; /* connect now */ if (client.connect(clientId.c_str())) { Serial.println("connected"); /* subscribe topic */ client.subscribe(LED_TOPIC); } else { Serial.print("failed, status code ="); Serial.print(client.state()); Serial.println("try again in 5 seconds"); /* Wait 5 seconds before retrying */ delay(5000); } } } void setup() { Serial.begin(115200); // We start by connecting to a WiFi network Serial.println(); Serial.print("Connecting to "); Serial.println(ssid); WiFi.begin(ssid, password); while (WiFi.status() != WL_CONNECTED) { delay(500); Serial.print("."); } /* set led as output to control led on-off */ pinMode(led, OUTPUT); Serial.println(""); Serial.println("WiFi connected"); Serial.println("IP address: "); Serial.println(WiFi.localIP()); /*setup MDNS for ESP32 */ if (!MDNS.begin("esp32")) { Serial.println("Error setting up MDNS responder!"); while(1) { delay(1000); } } /* get the IP address of server by MDNS name */ Serial.println("mDNS responder started"); IPAddress serverIp = MDNS.queryHost(serverHostname); Serial.print("IP address of server: "); Serial.println(serverIp.toString()); /* set SSL/TLS certificate */ espClient.setCACert(ca_cert); /* configure the MQTT server with IPaddress and port */ client.setServer(serverIp, 8883); /* this receivedCallback function will be invoked when client received subscribed topic */ client.setCallback(receivedCallback); } void loop() { /* if client was disconnected then try to reconnect again */ if (!client.connected()) { mqttconnect(); } /* this function will listen for incomming subscribed topic-process-invoke receivedCallback */ client.loop(); /* we increase counter every 3 secs we count until 3 secs reached to avoid blocking program if using delay()*/ long now = millis(); if (now - lastMsg > 3000) { lastMsg = now; if (counter < 100) { counter++; snprintf (msg, 20, "%d", counter); /* publish the message */ client.publish(COUNTER_TOPIC, msg); }else { counter = 0; } } }

3. Result