It works

src/mqtt.ino

@@ -0,0 +1,89 @@
+#include "inc/include.h"
+
+WiFiClient espClient;
+PubSubClient mqttClient(espClient);
+
+void mqttSendCommand(const char *msg) {
+  mqttClient.publish(MQTT_TOPIC_OUT, msg, 1);
+  DEBUG_F("[MQTT] Message sent: %s\n", msg);
+}
+
+void mqttSendStatus(const char *msg) {
+  mqttClient.publish(MQTT_TOPIC_STATUS, msg, 1);
+  DEBUG_F("[MQTT] Status sent: %s\n", msg);
+}
+
+void onMqttMsgReceived(char* topic, byte* payload, unsigned int len) {
+  if (len != 1) {
+    char* command = (char*)malloc(len + 2);
+    memcpy(command, payload, len);
+    command[len] = '\0';
+
+    DEBUG_F("[MQTT] Message received [%u]: %s\n", len, command);
+    return;
+  }
+
+  char cmd = (char)payload[0];
+  DEBUG_F("[MQTT] Command received: %c\n", cmd);
+
+  switch (cmd) {
+    case MSG_IN_OPEN:
+      action = OPEN;
+      break;
+
+    case MSG_IN_REJECT:
+      action = REJECT;
+      break;
+
+    case MSG_IN_PING:
+      mqttSendStatus(MSG_STATUS_READY);
+      break;
+
+    default:
+      DEBUG_LN("[MQTT] Unknown command");
+      break;
+  }
+}
+
+void mqttConnect() {
+  DEBUG_F("[MQTT] (Re)connecting to server on %s...\n", MQTT_SERVER_ADDR);
+
+  for (int i = 0; !mqttClient.connected(); i++) {
+    // Если не получилось за 5 попыток - перезагружаемся
+    if (i >= 5) {
+      ESP.restart();
+      return;
+    }
+
+    if (!mqttClient.connect(MQTT_CLIENT_ID, MQTT_USER_NAME, MQTT_USER_PASSWORD, MQTT_TOPIC_STATUS, 0, 0, MSG_STATUS_LAST_WILL)) {
+      // Ждем 2 секунды
+      DEBUG_F(".");
+      ledBlink(PIN_LED_GREEN, 8);
+    }
+  }
+
+  DEBUG_LN("\n[MQTT] Done");
+  mqttSendStatus(MSG_STATUS_READY);
+  mqttClient.subscribe(MQTT_TOPIC_IN);
+
+  setStateIdle();
+  DEBUG_LN("[MQTT] Current state: IDLE");
+}
+
+void mqttStop() {
+  mqttClient.disconnect();
+  ledOff();
+}
+
+void mqttSetup() {
+  mqttClient.setServer(MQTT_SERVER_ADDR, MQTT_SERVER_PORT);
+  mqttClient.setCallback(onMqttMsgReceived);
+  mqttConnect();
+}
+
+void mqttLoop() {
+  if (!mqttClient.connected()) {
+    mqttConnect();
+  }
+  mqttClient.loop();
+}