Studio Clock

A self-hosted broadcast clock and shared timer for live production environments. Displays an NTP-synced clock and a synchronized countdown timer that all connected clients see in real time.

Features

• NTP-synced clock — server queries pool.ntp.org and serves a corrected timestamp to all browsers, keeping every display in sync regardless of client clock drift
• Shared countdown timer — operator starts/pauses/resets the timer; all viewer screens update instantly via Server-Sent Events
• Operator / viewer modes — /operator shows timer controls, / (viewer) shows display only
• No dependencies — pure Node.js, no npm install required
• Docker support — single container, runs anywhere

Usage

Docker (recommended)

docker compose up -d

Direct

node server.js

The server runs on port 7823 by default (an uncommon port chosen to avoid conflicts). Set the PORT environment variable to override.

URL	Purpose
http://host:7823/	Viewer — display only
http://host:7823/operator	Operator — timer controls

Windows laptop (event use)

For running on a Windows laptop without Docker: install Node.js (LTS), then double-click:

• start.bat — starts the server in the background and opens the operator page in your browser
• stop.bat — stops the server

Windows Firewall may prompt to allow Node.js on first run — allow it if other devices (viewer screens) need to connect over the network. Display settings and saved presets live in presets.json/state.json next to server.js, so they persist across start.bat/stop.bat as long as you don't delete the folder.

How it works

• The server implements SNTP (RFC 4330) using Node's built-in dgram module — no external packages needed
• Timer state lives on the server; clients receive updates over a persistent SSE connection (/events) and send commands via POST
• Between SSE updates, running timers count down locally using the last known remaining value, so the display stays smooth without polling