A serverless monitoring solution for your home server with push notifications when it goes offline.

• Real-time Status: Check if your server is online/offline
• Push Notifications: Get notified when server goes down (1+ hour without heartbeat)
• PWA Support: Install as a Progressive Web App on mobile/desktop
• Clean Architecture: Static files served separately for better maintainability

heartbeat/
├── main.ts              # Hono server with API routes
├── index.html           # Static HTML page
├── client.js            # Frontend JavaScript
├── sw.js                # Service Worker for push notifications
├── monitor.ts           # Interval val that checks for downtime
├── generate-vapid-keys.ts  # Script to generate VAPID keys
└── README.md            # This file

Run the generate-vapid-keys.ts script to generate your VAPID keys.

Add these to your Val Town environment:

• VAPID_PUBLIC_KEY - Public key from step 1
• VAPID_PRIVATE_KEY - Private key from step 1

Add a cron job to your home server that pings the heartbeat endpoint every 15 minutes:

*/15 * * * * curl -X POST https://halffullheartbeat.val.run/heartbeat

1. Visit your deployed app
2. Click "Enable Notifications"
3. Grant notification permission

Your server calls this endpoint to signal it's alive.

Returns current server status:

{
  "lastHeartbeat": 1234567890000,
  "isOnline": true,
  "minutesSince": 5,
  "currentTime": 1234567890000
}

Subscribe to push notifications (called by frontend).

Get VAPID public key for push subscription.

1. Heartbeat: Your server sends a POST request every 15 minutes to /heartbeat
2. Monitoring: The monitor.ts interval val checks every 15 minutes if any heartbeat was received in the last hour
3. Notifications: If server is down (no heartbeat for 1+ hour), push notifications are sent to all subscribers
4. Status: Frontend polls /status every 30 seconds to show real-time status

This project now uses a clean separation of concerns:

• main.ts: Pure backend logic with Hono routes
• index.html: Static HTML served as-is (no React SSR needed)
• client.js: Frontend JavaScript in a separate file
• sw.js: Service Worker logic in its own file

Benefits:

• ✅ Better maintainability
• ✅ Easier debugging (proper file names in dev tools)
• ✅ Better caching (static files cached separately)
• ✅ No need for React imports or dangerouslySetInnerHTML
• ✅ Cleaner codebase

• Val Town: Serverless hosting
• Hono: Fast web framework
• SQLite: Database for heartbeats and subscriptions
• Push API: Browser push notifications
• Service Workers: Offline support and notifications