Support LWT messages when using TASMESH (#20392)

* Send LWTs when nodes come online and offline

* Use string macro

* Add a TASMESH_HEARTBEAT config

* Add flags to config file

* Fix missing break in case

* Rename heartbeat feature define

* Comment out tasmesh settings

* Detect online peers on all packets, not just heartbeats

tasmota/my_user_config.h

@@ -396,6 +396,8 @@
 
 // -- ESP-NOW -------------------------------------
 //#define USE_TASMESH                              // Enable Tasmota Mesh using ESP-NOW (+11k code)
+//#define USE_TASMESH_HEARTBEAT                    // If enabled, the broker will detect when nodes come online and offline and send Birth and LWT messages over MQTT correspondingly
+//#define TASMESH_OFFLINE_DELAY  3                 // Maximum number of seconds since the last heartbeat before the broker considers a node to be offline
 
 // -- OTA -----------------------------------------
 //#define USE_ARDUINO_OTA                          // Add optional support for Arduino OTA with ESP8266 (+13k code)

tasmota/tasmota_xdrv_driver/xdrv_57_1_tasmesh_support.ino

@@ -91,6 +91,10 @@ struct mesh_peer_t {
   uint32_t lastMessageFromPeer;    // Time of last message from peer
 #ifdef ESP32
   char topic[MESH_TOPICSZ];
+#ifdef USE_TASMESH_HEARTBEAT
+  bool isAlive;                    // True if we have gotten a heartbeat recently
+  uint32_t lastHeartbeatFromPeer;  // Time of last heartbeat from peer
+#endif // USE_TASMESH_HEARTBEAT
 #endif //ESP32
 };
 
@@ -164,7 +168,10 @@ enum MESH_Packet_Type {            // Type of packet
   PACKET_TYPE_REGISTER_NODE,       // register a node with encrypted broker-MAC, announce mqtt topic to ESP32-proxy - broker will send time ASAP
   PACKET_TYPE_REFRESH_NODE,        // refresh node infos with encrypted broker-MAC, announce mqtt topic to ESP32-proxy - broker will send time slightly delayed
   PACKET_TYPE_MQTT,                // send regular mqtt messages, single or multipackets
-  PACKET_TYPE_WANTTOPIC            // the broker has no topic for this peer/node
+  PACKET_TYPE_WANTTOPIC,           // the broker has no topic for this peer/node
+#ifdef USE_TASMESH_HEARTBEAT
+  PACKET_TYPE_HEARTBEAT            // sent periodically from nodes to the broker to signal aliveness
+#endif // USE_TASMESH_HEARTBEAT
 };
 
 /*********************************************************************************************\

tasmota/tasmota_xdrv_driver/xdrv_57_9_tasmesh.ino

@@ -472,6 +472,22 @@ void MESHevery50MSecond(void) {
     // do something on the node
     // AddLog(LOG_LEVEL_DEBUG, PSTR("MSH: %30_H), (uint8_t *)&MESH.packetToConsume.front());
 
+#ifdef USE_TASMESH_HEARTBEAT
+    for (auto &_peer : MESH.peers){
+      if (memcmp(_peer.MAC, MESH.packetToConsume.front().sender, 6) == 0) {
+        _peer.lastHeartbeatFromPeer = millis();
+
+        if (!_peer.isAlive) {
+          _peer.isAlive = true;
+          char stopic[TOPSZ];
+          GetTopic_P(stopic, TELE, _peer.topic, S_LWT);
+          MqttPublishPayload(stopic, PSTR(MQTT_LWT_ONLINE));
+        }
+        break;
+      }
+    }
+#endif // USE_TASMESH_HEARTBEAT
+
     MESHencryptPayload(&MESH.packetToConsume.front(), 0);
     switch (MESH.packetToConsume.front().type) {
       // case PACKET_TYPE_REGISTER_NODE:
@@ -546,6 +562,9 @@ void MESHevery50MSecond(void) {
 //          AddLog(LOG_LEVEL_INFO, PSTR("MSH: %*_H), MESH.packetToConsume.front().chunkSize, (uint8_t *)&MESH.packetToConsume.front().payload);
         }
         break;
+      case PACKET_TYPE_HEARTBEAT:
+        break;
+
       default:
         AddLogBuffer(LOG_LEVEL_DEBUG, (uint8_t *)&MESH.packetToConsume.front(), MESH.packetToConsume.front().chunkSize +5);
       break;
@@ -582,6 +601,17 @@ void MESHEverySecond(void) {
     AddLog(LOG_LEVEL_INFO, PSTR("MSH: Multi packets in buffer %u"), MESH.multiPackets.size());
     MESH.multiPackets.erase(MESH.multiPackets.begin());
   }
+
+#ifdef USE_TASMESH_HEARTBEAT
+  for (auto &_peer : MESH.peers){
+    if (_peer.isAlive && TimePassedSince(_peer.lastHeartbeatFromPeer) > TASMESH_OFFLINE_DELAY * 1000) {
+      _peer.isAlive = false;
+      char stopic[TOPSZ];
+      GetTopic_P(stopic, TELE, _peer.topic, S_LWT);
+      MqttPublishPayload(stopic, PSTR(MQTT_LWT_OFFLINE));
+    }
+  }
+#endif // USE_TASMESH_HEARTBEAT
 }
 
 #else  // ESP8266
@@ -649,6 +679,16 @@ void MESHEverySecond(void) {
       MESHsetWifi(1);
       WifiBegin(3, MESH.channel);
     }
+
+#ifdef USE_TASMESH_HEARTBEAT
+    MESH.sendPacket.counter++;
+    MESH.sendPacket.TTL = 2;
+    MESH.sendPacket.chunks = 0;
+    MESH.sendPacket.chunk = 0;
+    MESH.sendPacket.chunkSize = 0;
+    MESH.sendPacket.type = PACKET_TYPE_HEARTBEAT;
+    MESHsendPacket(&MESH.sendPacket);
+#endif // USE_TASMESH_HEARTBEAT
   }
 }