Automatic Device Discovery (mDNS)

How mDNS Discovery Works

TOMMY Instance Advertisement

When the TOMMY instance starts (Home Assistant add-on or Docker):

1. Service Advertisement: TOMMY instance advertises itself as _tommy._tcp.local service via mDNS
2. Network Information: Broadcasts its IP address and required ports
3. Service Details: Includes metadata like version, startup time, and process ID

Device Discovery Process

1. Network Listening: Devices with TOMMY firmware listen for _tommy._tcp.local broadcasts
2. Instance Detection: When devices detect the TOMMY instance advertisement, they extract:
   • Instance IP Address: Where to send data and heartbeats
   • Communication Ports: MQTT, file server, and other service ports
   • Service Availability: Confirms TOMMY instance is running and accessible
3. Automatic Connection: Devices automatically connect to the discovered TOMMY instance
4. Dashboard Integration: Connected devices appear in the TOMMY dashboard within seconds

Requirements for mDNS Discovery

Network Configuration

• Same Network Segment: TOMMY instance and devices must be on the same network
• mDNS Support: Network infrastructure must allow multicast traffic
• No mDNS Blocking: Firewall or router settings must permit mDNS packets

Compatible Networks

Works Well With:

• Home Wi-Fi networks
• Simple router setups
• Mesh networks (most configurations)
• Unmanaged switches

May Have Issues With:

• Enterprise networks with mDNS filtering
• VLANs with multicast restrictions
• Some managed switches with IGMP snooping
• Networks with aggressive multicast filtering

Troubleshooting Automatic Discovery

Device Not Appearing

If your device doesn't appear in the dashboard:

1. Check TOMMY Instance

   • Verify TOMMY instance is running and accessible
   • Ensure TOMMY has started successfully (check logs)
   • Confirm mDNS advertisement is active

2. Check Device Network Connection

   • Verify device connected to Wi-Fi (check router's connected devices)
   • Ensure device and TOMMY are on same network segment

3. Verify mDNS Functionality

   • Test with other mDNS services (like AirPlay or Chromecast)
   • Check if router supports multicast/broadcast traffic
   • Ensure no firewall is blocking port 5353 (mDNS port)