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Flutter App Connection

The Flutter app communicates with Pi 1 over the WiFi access point (DroneCommandNet). Pi 1 then relays commands to the other drones over the BATMAN-adv mesh.

Architecture

The app connects to Pi 1 on port 5001 and Pi 1 connects back to the app on port 5100 to send data.

Configuration

Pi 1 — mission_config.json

{
  "app_opperable": true,
  "drone_info": [
    { "id": 1, "IP": "169.254.97.1", "port": 5001 },
    { "id": 2, "IP": "169.254.97.2", "port": 5002 },
    { "id": 3, "IP": "169.254.97.3", "port": 5003 },
    { "id": 4, "IP": "169.254.97.4", "port": 5004 }
  ],
  "app_info": {
    "ip": "192.168.50.X",
    "port": 5100
  }
}

Replace 192.168.50.X with the phone’s IP address. To find it:

cat /var/lib/misc/dnsmasq.leases

Note: mission_config.json is automatically updated on boot by the startup script to set the correct mesh IPs. The app_info IP may need to be updated manually if the phone’s IP changes.

Pi 1 — server.py

The server binds to 0.0.0.0 so it accepts connections from both the app (via wlan1) and other drones (via bat0):

server = await asyncio.start_server(
    self.handle_client,
    "0.0.0.0",
    self.networkConfig.get_drone_port(self.droneId),
)

Flutter App — networking.dart

final InternetAddress externalIp = InternetAddress('192.168.50.1');
final int externalPort = 5001;
final int listenPort = 5100;

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Testing the Connection

1. Verify Pi 1 is listening

sudo ss -tulnp | grep 5001

Should show main.py listening on 0.0.0.0:5001.

2. Connect phone to DroneCommandNet

The phone should get a 192.168.50.x IP address.

3. Ping the phone from Pi 1

ping -c 4 192.168.50.X

4. Open the Flutter app

The app will automatically attempt to connect to 192.168.50.1:5001.

5. Monitor Pi 1 for incoming connections

Stop the background service and run main.py manually to see real-time output:

sudo systemctl stop batman-net.service
sudo bash -c 'cd /home/mrrdt-1/IARC-10 && uv run main.py -i 1'

You should see connection and message activity in the terminal when the app connects.

Message Protocol

The app and Pi 1 communicate using JSON messages over raw TCP sockets. Each message has the following structure:

{
  "id": 401,
  "dronesToSendData": [1],
  "data": {}
}

Troubleshooting

App can’t connect to Pi 1

• Verify phone is connected to DroneCommandNet and has a 192.168.50.x IP
• Verify Pi 1 is listening: sudo ss -tulnp | grep 5001
• Check app_opperable is true in mission_config.json
• Check main.py is running: ps aux | grep main.py

App connects but no data received

• Check app_info IP in mission_config.json matches the phone’s actual IP
• The phone’s IP can change between connections — check with cat /var/lib/misc/dnsmasq.leases

Pi 1 can’t send data back to app

• Pi 1 uses app_info.ip and app_info.port to connect back to the app
• Make sure app_info.port matches listenPort in the Flutter app (5100)
• Make sure app_info.ip matches the phone’s current IP on DroneCommandNet