Add testing config explanation to README

README.md

@@ -126,7 +126,52 @@ LOGGING=0
 
 > **Reminder**: The .env file is duplicated across both dashboard/ and simulator/ — keep them in >sync if you make changes.
 
+## Testing Without the Real Factory
 
+If the physical Fischertechnik factory is offline, you can still run a full end-to-end demo by spinning up a **second Mosquitto broker** that pretends to be the “real” system.
+
+### 1  Start an additional broker on port 1884
+
+```bash
+# Start a second Mosquitto instance (on Linux/macOS)
+mosquitto -p 1884 -v &
+```
+Or use a separate terminal window. This lets you simulate real factory messages independently from the simulation broker (which runs on 1883).
+
+### 2  Configure both brokers via `.env`
+
+Edit the `.env` file in **both** `dashboard/` and `simulator/`:
+
+```ini
+# Simulated MQTT broker (used for internal DEVS comms + dashboard visualizations)
+MQTT_SIM_HOST=127.0.0.1
+MQTT_SIM_PORT=1883
+
+# Real factory MQTT broker (used to inject real-world-like events)
+MQTT_REAL_HOST=127.0.0.1
+MQTT_REAL_PORT=1884
+
+# Optional logging toggle
+LOGGING=0
+```
+
+### 3  Run the components as usual
+ 
+```bash
+./run_sim.sh         # Connects to both brokers (1883 + 1884)
+./run_dashboard.sh   # Connects to both brokers (1883 + 1884)
+```
+
+This setup gives you:
+
+
+| Port     | Role                       | Used by                                                                       |
+| -------- | -------------------------- | ----------------------------------------------------------------------------- |
+| **1883** | Simulation broker          | Simulator ✅ (internal messages)<br>Dashboard ✅ (monitoring + visualization) |
+| **1884** | “Fake real factory” broker | Simulator ✅ (real events injection)<br>Dashboard ✅ (monitoring)             |
+
+
+The simulator uses **1883** for simulation-specific MQTT commands (like `simulation/ctrl/...`, visualization output, etc.), and **1884** to receive simulated “real factory” messages like new workpiece arrivals or workpiece orders.
 
 ## Project Structure