Add EthernetMQTT example to demonstrate mTLS (credit @Atalonica)

examples/EthernetMQTT/EthernetMQTT.ino

@@ -0,0 +1,87 @@
+/*
+ Basic MQTT example (with SSL!)
+ This sketch demonstrates the basic capabilities of the library.
+ It connects to an MQTT server then:
+  - publishes "hello world" to the topic "outTopic"
+  - subscribes to the topic "inTopic", printing out any messages
+    it receives. NB - it assumes the received payloads are strings not binary
+ It will reconnect to the server if the connection is lost using a blocking
+ reconnect function. See the 'mqtt_reconnect_nonblocking' example for how to
+ achieve the same result without blocking the main loop.
+
+ You will need to populate "certificates.h" with your trust anchors
+ (see https://github.com/OPEnSLab-OSU/SSLClient/blob/master/TrustAnchors.md)
+ and my_cert/my_key with your certificate/private key pair
+ (see https://github.com/OPEnSLab-OSU/SSLClient#mtls).
+*/
+#include <SPI.h>
+#include <EthernetLarge.h>
+#include <SSLClient.h>
+#include "certificates.h" // This file must be regenerated
+#include <PubSubClient.h>
+
+const char my_cert[] = "FIXME";
+const char my_key[] = "FIXME";
+SSLClientParameters mTLS = SSLClientParameters::fromPEM(my_cert, sizeof my_cert, my_key, sizeof my_key);
+
+byte mac[] = {  0xDE, 0xED, 0xBA, 0xFE, 0xFE, 0xED };
+const char* mqttServer = "broker.example"; // Broker address
+IPAddress ip (192, 168, 1, 2); // Custom client static IP
+
+void callback(char* topic, byte* payload, unsigned int length) {
+  Serial.print("Message arrived [");
+  Serial.print(topic);
+  Serial.print("] ");
+  for (int i=0;i<length;i++) {
+    Serial.print((char)payload[i]);
+  }
+  Serial.println();
+}
+
+EthernetClient ethClient;
+SSLClient ethClientSSL(ethClient, TAs, (size_t)TAs_NUM, A5);
+PubSubClient client(mqttServer, 8883, callback, ethClientSSL);
+
+void reconnect() {
+  // Loop until we're reconnected
+  while (!client.connected()) {
+    Serial.print("Attempting MQTT connection...");
+    // Attempt to connect
+    if (client.connect("arduinoClient")) {
+      Serial.println("connected");
+      // Once connected, publish an announcement...
+      client.publish("outTopic","hello world");
+      // ... and resubscribe
+      client.subscribe("inTopic");
+    } else {
+      Serial.print("failed, rc=");
+      Serial.print(client.state());
+      Serial.println(" try again in 5 seconds");
+      // Wait 5 seconds before retrying
+      delay(5000);
+    }
+  }
+}
+
+void setup(){
+  // Start Serial
+  Serial.begin(115200);
+  while(!Serial);
+  // Enable mutual TLS with SSLClient
+  ethClientSSL.setMutualAuthParams(mTLS);
+  // You can use Ethernet.init(pin) to configure the CS pin
+  Ethernet.init(10);  // Most Arduino shields
+  //Ethernet.init(5);   // MKR ETH shield
+  //Ethernet.init(0);   // Teensy 2.0
+  //Ethernet.init(20);  // Teensy++ 2.0
+  //Ethernet.init(15);  // ESP8266 with Adafruit Featherwing Ethernet
+  //Ethernet.init(33);  // ESP32 with Adafruit Featherwing Ethernet
+  Ethernet.begin(mac, ip);
+}
+
+void loop(){
+  if (!client.connected()) {
+    reconnect();
+  }
+  client.loop();
+}