adding discovery request and moving HB to its own function

app/node_main.py

@@ -129,6 +129,7 @@ async def mqtt_lifecycle_manager():
         if rc == 0:
             LOGGER.info(f"Connected to MQTT Broker: {MQTT_BROKER}")
             client.subscribe(f"nodes/{NODE_ID}/commands")
+            client.subscribe("nodes/discovery/request")
             MQTT_CONNECTED = True
         else:
             LOGGER.error(f"MQTT Connection failed: {rc}")
@@ -139,7 +140,32 @@ async def mqtt_lifecycle_manager():
         if rc != 0:
             LOGGER.warning("Unexpected MQTT disconnection.")
 
+    def publish_heartbeat():
+        """Helper to gather status and publish check-in."""
+        try:
+            status_response = requests.get("http://localhost:8001/op25/status", timeout=2)
+            op25_status = status_response.json() if status_response.ok else {}
+        except Exception:
+            op25_status = {"is_running": False}
+
+        payload = {
+            "node_id": NODE_ID,
+            "status": "online",
+            "timestamp": datetime.now().isoformat(),
+            "is_listening": op25_status.get("is_running", False),
+            "active_system": op25_status.get("active_system"),
+            # Only scan library if needed, otherwise it's heavy I/O
+            "available_systems": scan_local_library() 
+        }
+
+        client.publish(f"nodes/{NODE_ID}/checkin", json.dumps(payload), retain=True)
+        LOGGER.debug("Sent Heartbeat/Check-in")
+
     def on_message(client, userdata, msg):
+        if msg.topic == "nodes/discovery/request":
+            LOGGER.info("Received Discovery Request. Sending Heartbeat...")
+            publish_heartbeat()
+        else:
             handle_c2_command(msg.topic, msg.payload.decode())
 
     # --- Setup ---
@@ -158,28 +184,9 @@ async def mqtt_lifecycle_manager():
         # --- Main Heartbeat Loop ---
         while True:
             if MQTT_CONNECTED:
-                # 1. Gather Data (This was previously in on_connect)
-                try:
-                    status_response = requests.get("http://localhost:8001/op25/status", timeout=2)
-                    op25_status = status_response.json() if status_response.ok else {}
-                except Exception:
-                    op25_status = {"is_running": False}
-
-                payload = {
-                    "node_id": NODE_ID,
-                    "status": "online",
-                    "timestamp": datetime.now().isoformat(),
-                    "is_listening": op25_status.get("is_running", False),
-                    "active_system": op25_status.get("active_system"),
-                    # Only scan library if needed, otherwise it's heavy I/O
-                    "available_systems": scan_local_library() 
-                }
-
-                # 2. Publish Heartbeat (Acts as both check-in and keep-alive)
-                client.publish(f"nodes/{NODE_ID}/checkin", json.dumps(payload), retain=True)
-                LOGGER.debug("Sent Heartbeat/Check-in")
-            
+                publish_heartbeat()
                 # Pulse every 30 seconds
+                # Only wait 30 sec if the HB sent. This way we don't stall a check-in
                 await asyncio.sleep(30)
 
     except asyncio.CancelledError: