diff --git a/examples/arduino/w5500-http/mongoose_config.h b/examples/arduino/w5500-http/mongoose_config.h
index a42cf006..940edf63 100644
--- a/examples/arduino/w5500-http/mongoose_config.h
+++ b/examples/arduino/w5500-http/mongoose_config.h
@@ -14,5 +14,5 @@
 #define MG_ENABLE_TCPIP_PRINT_DEBUG_STATS 0
 #define MG_ENABLE_CUSTOM_MILLIS 1
 #define MG_ENABLE_CUSTOM_RANDOM 1
-// #define MG_TLS MG_TLS_BUILTIN
-#define MG_IO_SIZE 128
+#define MG_TLS MG_TLS_BUILTIN
+#define MG_IO_SIZE 256
diff --git a/examples/arduino/w5500-http/w5500-http.ino b/examples/arduino/w5500-http/w5500-http.ino
index d1be1a8c..f2171d9e 100644
--- a/examples/arduino/w5500-http/w5500-http.ino
+++ b/examples/arduino/w5500-http/w5500-http.ino
@@ -1,8 +1,8 @@
 #include <SPI.h>
 #include "mongoose.h"
 
-#define LED_PIN LED_BUILTIN  // LED pin - can be LED_BUILTIN
-#define SS_PIN 17    // Slave select pin
+#define LED_PIN LED_BUILTIN  // LED pin
+#define SS_PIN 17            // Slave select pin for the W5500 module
 
 struct mg_tcpip_spi spi = {
     NULL,  // SPI metadata
@@ -13,10 +13,12 @@ struct mg_tcpip_spi spi = {
 struct mg_mgr mgr;                                     // Mongoose event manager
 struct mg_tcpip_if mif = {.mac = {2, 0, 1, 2, 3, 5}};  // Network interface
 
+// Used by Mongoose for time tracking
 uint64_t mg_millis(void) {
   return millis();
 }
 
+// Used by Mongoose to generate random data
 bool mg_random(void *buf, size_t len) {  // For TLS
   uint8_t *p = (uint8_t *) buf;
   while (len--) *p++ = (unsigned char) (rand() & 255);
@@ -24,11 +26,63 @@ bool mg_random(void *buf, size_t len) {  // For TLS
 }
 
 // Crude function to get available RAM, for quick profiling
-size_t getFreeRAM(void) {
-  size_t size = 0, increment = 100;
-  void *p;
-  while ((p = malloc(size)) != NULL) free(p), size += increment;
-  return size;
+extern "C" char *sbrk(int);
+extern char *__brkval;
+int getFreeRAM() {
+  char top;
+#ifdef __arm__
+  return &top - (char *) sbrk(0);
+#elif defined(CORE_TEENSY) || (ARDUINO > 103 && ARDUINO != 151)
+  return &top - __brkval;
+#else
+  return __brkval ? &top - __brkval : &top - __malloc_heap_start;
+#endif
+}
+
+static void http_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
+  if (ev == MG_EV_HTTP_MSG) {
+    struct mg_http_message *hm = (struct mg_http_message *) ev_data;
+    if (mg_match(hm->uri, mg_str("/api/led/on"), NULL)) {
+      digitalWrite(LED_PIN, HIGH);
+      mg_http_reply(c, 200, "", "{%m: %d}\n", MG_ESC("led"), digitalRead(LED_PIN));
+    } else if (mg_match(hm->uri, mg_str("/api/led/off"), NULL)) {
+      digitalWrite(LED_PIN, LOW);
+      mg_http_reply(c, 200, "", "{%m: %d}\n", MG_ESC("led"), digitalRead(LED_PIN));
+    } else {
+      mg_http_reply(c, 200, "", "ok, free RAM: %u\n", getFreeRAM());
+    }
+  }
+  // Initialise TLS if we're a TLS listener
+  if (ev == MG_EV_ACCEPT && c->fn_data != NULL) {
+    struct mg_tls_opts opts;
+    memset(&opts, 0, sizeof(opts));
+
+    // Generated by https://mongoose.ws/tls/
+#define TLS_CERT \
+  "-----BEGIN CERTIFICATE-----\n" \
+  "MIIBkzCCATqgAwIBAgIEZ3E9lzAKBggqhkjOPQQDAjATMREwDwYDVQQDEwhNb25n\n" \
+  "b29zZTAeFw0yNDEyMjkxMjE2MjNaFw0zNDEyMjcxMjE2MjNaMBQxEjAQBgNVBAMT\n" \
+  "CWxvY2FsaG9zdDBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABHxxuByu5K2k7DYq\n" \
+  "b3eQsHb3VY5NWglWun7axh69OWF7V9OUUyON1y8ISirL0Gj5ZPOogIgrB9iOcz6K\n" \
+  "q9n8NQOjezB5MA4GA1UdDwEB/wQEAwIFoDATBgNVHSUEDDAKBggrBgEFBQcDATAM\n" \
+  "BgNVHRMBAf8EAjAAMB8GA1UdIwQYMBaAFGn8GpPWaM0JC7U4zlg+bCljSjLoMCMG\n" \
+  "A1UdEQQcMBqCCWxvY2FsaG9zdIINMTkyLjE2OC4wLjEwMDAKBggqhkjOPQQDAgNH\n" \
+  "ADBEAiAr1fO3QLLm+vjYarctNI+gfnxxB4edRTRmcFWHmBS8oQIgY5lkq2JCwATG\n" \
+  "YsVQUmS+2Tbc7ij7lkduXO42pvr/0fw=\n" \
+  "-----END CERTIFICATE-----"
+
+  #define TLS_KEY \
+  "-----BEGIN EC PRIVATE KEY-----\n" \
+  "MHcCAQEEIHKu84eEw9dX8nez82g3F94OsZJ14LVbAN+OBW+++V2poAoGCCqGSM49\n" \
+  "AwEHoUQDQgAEfHG4HK7kraTsNipvd5CwdvdVjk1aCVa6ftrGHr05YXtX05RTI43X\n" \
+  "LwhKKsvQaPlk86iAiCsH2I5zPoqr2fw1Aw==\n" \
+  "-----END EC PRIVATE KEY-----"
+
+    opts.cert = mg_str(TLS_CERT);
+    opts.key = mg_str(TLS_KEY);
+
+    mg_tls_init(c, &opts);
+  }
 }
 
 void setup() {
@@ -46,24 +100,9 @@ void setup() {
   mif.driver_data = &spi;               // Pass SPI interface to W5500 driver
   mg_tcpip_init(&mgr, &mif);            // Initialise built-in TCP/IP stack
 
-  // Setup HTTP listener. Respond "ok" on any HTTP request
-  mg_http_listen(
-      &mgr, "http://0.0.0.0",
-      [](struct mg_connection *c, int ev, void *ev_data) {
-        if (ev == MG_EV_HTTP_MSG) {
-          struct mg_http_message *hm = (struct mg_http_message *) ev_data;
-          if (mg_match(hm->uri, mg_str("/api/led/on"), NULL)) {
-            digitalWrite(LED_PIN, HIGH);
-            mg_http_reply(c, 200, "", "{%m: %d}\n", MG_ESC("led"), digitalRead(LED_PIN));
-          } else if (mg_match(hm->uri, mg_str("/api/led/off"), NULL)) {
-            digitalWrite(LED_PIN, LOW);
-            mg_http_reply(c, 200, "", "{%m: %d}\n", MG_ESC("led"), digitalRead(LED_PIN));
-          } else {
-            mg_http_reply(c, 200, "", "ok, free RAM: %u\n", getFreeRAM());
-          }
-        }
-      },
-      &mgr);
+  // Setup HTTP & HTTPS listeners. Respond "ok" on any HTTP request
+  mg_http_listen(&mgr, "http://0.0.0.0:80", http_ev_handler, NULL);
+  mg_http_listen(&mgr, "https://0.0.0.0:443", http_ev_handler, (void *) 1);
 }
 
 void loop() {