new example mqtt_airlift_subscribe_time_keepalive.ino

This approach stabilizes long-running MQTT connections on AirLift boards and prevents the “No socket available” disconnect condition that users are encountering.

Author: mikeysklar

examples/mqtt_airlift_subscribe_time_keepalive/mqtt_airlift_subscribe_time_keepalive.ino

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+/***************************************************
+  mqtt_airlift_subscribe_time_keepalive
+
+  Example demonstrating MQTT subscription and manual
+  KeepAlive handling for AirLift (ESP32 / NINA-FW)
+  devices using the Adafruit_MQTT_Library.
+
+  This example:
+    * Connects an AirLift device to WiFi
+    * Subscribes to io.adafruit.com/time/ISO-8601
+    * Manually manages MQTT KeepAlive intervals
+    * Sends periodic MQTT PINGs to maintain the
+      MQTT session (workaround for NINA-FW behavior)
+
+  Written by Bruce Conrad.
+  MIT license, all text above must be included in
+  any redistribution.
+ ****************************************************/
+
+#include <SPI.h>
+#include <WiFiNINA.h>
+#include "Adafruit_MQTT.h"
+#include "Adafruit_MQTT_Client.h"
+
+/************************* WiFi Setup *********************************/
+// Update for your WiFi network.
+#define WIFI_SSID   "YOUR_WIFI_SSID"
+#define WIFI_PASS   "YOUR_WIFI_PASSWORD"
+
+/************************* Adafruit IO Setup ***************************/
+#define AIO_SERVER      "io.adafruit.com"
+#define AIO_SERVERPORT  1883      // use 8883 for MQTTS
+#define AIO_USERNAME    "YOUR_ADAFRUIT_IO_USERNAME"
+#define AIO_KEY         "YOUR_ADAFRUIT_IO_KEY"
+
+/************************* AirLift Pin Setup ***************************/
+// These are the pins you provided and known-good.
+#define SPIWIFI       SPI
+#define SPIWIFI_SS    13
+#define SPIWIFI_IRQ   11
+#define SPIWIFI_RESET 12
+#define ESP32_GPIO0   -1
+
+/*************************** Timing / Params ***************************/
+#define AIRLIFT_KEEPALIVE   30
+#define MAX_MQTT_RETRIES    5
+#define SUBSCRIBE_WAIT_MS   1500
+#define PING_PERIOD_MS      ((AIRLIFT_KEEPALIVE - 10) * 1000)
+
+/*************************** MQTT Objects ******************************/
+WiFiClient client;
+
+Adafruit_MQTT_Client mqtt(
+  &client,
+  AIO_SERVER,
+  AIO_SERVERPORT,
+  AIO_USERNAME,
+  AIO_KEY
+);
+
+Adafruit_MQTT_Subscribe time_subscription =
+  Adafruit_MQTT_Subscribe(&mqtt, "time/ISO-8601");
+
+/*************************** State Vars *******************************/
+unsigned long ping_clk = 0;
+long ping_cnt = 0;
+
+/*************************** Function Prototypes ***********************/
+void initWiFi();
+void MQTT_connect();
+void MQTT_ping();
+void printCurrentNet();
+void printWiFiData();
+void printMacAddress(byte mac[]);
+
+/*************************** Setup *************************************/
+void setup() {
+  Serial.begin(115200);
+  while (!Serial) delay(10);
+
+  Serial.println("MQTT AirLift Subscribe + KeepAlive Example");
+
+  initWiFi();
+
+  mqtt.setKeepAliveInterval(AIRLIFT_KEEPALIVE);
+  mqtt.subscribe(&time_subscription);
+
+  MQTT_connect();
+}
+
+/*************************** Main Loop *********************************/
+void loop() {
+
+  MQTT_ping();
+
+  Adafruit_MQTT_Subscribe *subscription =
+    mqtt.readSubscription(SUBSCRIBE_WAIT_MS);
+
+  if (subscription == &time_subscription) {
+    Serial.print("TIME FEED: ");
+    Serial.println((char *)time_subscription.lastread);
+  }
+}
+
+/*************************** MQTT Connect ******************************/
+void MQTT_connect() {
+
+  unsigned long start = millis();
+  long attempts = 0;
+
+  while (attempts < MAX_MQTT_RETRIES) {
+    attempts++;
+
+    Serial.print("MQTT Connect Attempt #");
+    Serial.print(attempts);
+    Serial.print(" ... ");
+
+    int8_t ret = mqtt.connect();
+
+    if (ret == 0) {
+      Serial.print("Connected in ");
+      Serial.print(millis() - start);
+      Serial.println(" ms");
+      ping_clk = millis();
+      return;
+    }
+
+    Serial.println(mqtt.connectErrorString(ret));
+    Serial.println("Retrying in 5 seconds...");
+    mqtt.disconnect();
+    delay(5000);
+  }
+
+  Serial.println("ERROR: Maximum MQTT connect attempts exceeded.");
+  while (1) delay(10);
+}
+
+/*************************** MQTT PING Logic ***************************/
+void MQTT_ping() {
+  if ((millis() - ping_clk) < PING_PERIOD_MS) return;
+
+  ping_cnt++;
+  unsigned long start = millis();
+
+  Serial.print("PING #");
+  Serial.print(ping_cnt);
+  Serial.print(" ... ");
+
+  for (int i = 0; i < MAX_MQTT_RETRIES; i++) {
+
+    if (mqtt.ping()) {
+      Serial.print("OK (");
+      Serial.print(millis() - start);
+      Serial.println(" ms)");
+      ping_clk = millis();
+      return;
+    }
+
+    Serial.print("fail ");
+    delay(1000);
+  }
+
+  Serial.println("\nERROR: No MQTT PING response. Halting.");
+  while (1) delay(10);
+}
+
+/*************************** WiFi Init *********************************/
+void initWiFi() {
+
+  // IMPORTANT: passes the *SPI object* (SPIWIFI), not a pin
+  WiFi.setPins(SPIWIFI_SS, SPIWIFI_IRQ, SPIWIFI_RESET, ESP32_GPIO0, &SPIWIFI);
+
+  Serial.println("Starting AirLift WiFi...");
+
+  if (WiFi.status() == WL_NO_SHIELD) {
+    Serial.println("ERROR: Communication with AirLift failed.");
+    while (1) delay(10);
+  }
+
+  Serial.print("NINA-FW Version: ");
+  Serial.println(WiFi.firmwareVersion());
+
+  int status = WL_IDLE_STATUS;
+
+  while (status != WL_CONNECTED) {
+    Serial.print("Connecting to SSID: ");
+    Serial.println(WIFI_SSID);
+
+    status = WiFi.begin(WIFI_SSID, WIFI_PASS);
+
+    while (WiFi.localIP()[0] == 0) {
+      delay(50);
+    }
+  }
+
+  Serial.println("WiFi connected.");
+  printCurrentNet();
+  printWiFiData();
+}
+
+/*************************** Helpers ***********************************/
+void printCurrentNet() {
+  Serial.print("SSID: ");
+  Serial.print(WiFi.SSID());
+
+  byte bssid[6];
+  WiFi.BSSID(bssid);
+
+  Serial.print("  BSSID: ");
+  printMacAddress(bssid);
+
+  Serial.print("  RSSI: ");
+  Serial.print(WiFi.RSSI());
+
+  Serial.print("  Encryption: ");
+  Serial.println(WiFi.encryptionType(), HEX);
+}
+
+void printWiFiData() {
+  Serial.print("IP: ");
+  Serial.print(WiFi.localIP());
+
+  Serial.print("  Gateway: ");
+  Serial.print(WiFi.gatewayIP());
+
+  Serial.print("  Subnet: ");
+  Serial.print(WiFi.subnetMask());
+
+  byte mac[6];
+  WiFi.macAddress(mac);
+
+  Serial.print("  MAC: ");
+  printMacAddress(mac);
+}
+
+void printMacAddress(byte mac[]) {
+  for (int i = 5; i >= 0; i--) {
+    if (mac[i] < 16) Serial.print("0");
+    Serial.print(mac[i], HEX);
+    if (i > 0) Serial.print(":");
+  }
+  Serial.print(" ");
+}