SSE Server (EventSource)

beginner

Simple Server-Sent Events development server.

Overview

Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine that enables server-side JavaScript execution. Originally created by Ryan Dahl in 2009, Node.js revolutionized web development by allowing developers to use JavaScript for both client and server-side code. Its event-driven, non-blocking I/O model makes it particularly well-suited for real-time applications and data-intensive tasks that require high concurrency. This Docker configuration creates a lightweight Server-Sent Events (SSE) development server using Node.js on Alpine Linux. The setup provides a minimal foundation for building real-time, one-way communication from server to client using the EventSource API. Unlike WebSockets which require bidirectional communication, this Node.js SSE server focuses specifically on pushing data from server to browser clients with automatic reconnection and built-in event handling. Developers building real-time dashboards, live notifications, or streaming data applications will find this configuration particularly valuable. The combination of Node.js's event loop architecture and SSE's simplicity creates an efficient solution for applications that need to push updates to multiple clients simultaneously without the complexity of full WebSocket implementations.

Key Features

Node.js 20 Alpine Linux base image for minimal resource footprint and enhanced security
Built-in EventSource API support with automatic client reconnection on connection drops
Non-blocking I/O event loop architecture optimized for concurrent client connections
Native text/event-stream content type handling for proper SSE protocol compliance
Automatic event ID sequencing and last-event-id tracking for reliable message delivery
Hot-reload development environment with volume mounting for rapid iteration
Cross-origin resource sharing (CORS) compatibility for browser-based clients
Memory-efficient streaming without buffering large datasets

Common Use Cases

1Real-time dashboard updates for system monitoring and analytics visualization
2Live notification systems for social media applications and messaging platforms
3Financial market data streaming for trading platforms and investment tools
4IoT sensor data broadcasting to multiple connected devices and monitoring systems
5Live sports scores and game updates for sports applications and websites
6Server log streaming and debugging tools for development teams
7Chat application message broadcasting and presence indicators

Prerequisites

Docker and Docker Compose installed on the host system
Port 3000 available on the host machine for the SSE server
Basic JavaScript and Node.js knowledge for server implementation
Understanding of EventSource API and browser-based event handling
Minimum 512MB RAM available for Node.js runtime and application code
Local ./app directory with server.js file containing SSE implementation

For development & testing. Review security settings, change default credentials, and test thoroughly before production use. See Terms

docker-compose.yml

1services: 
2  sse-server: 
3    image: node:20-alpine
4    container_name: sse-server
5    restart: unless-stopped
6    working_dir: /app
7    command: node server.js
8    volumes: 
9      - ./app:/app
10    ports: 
11      - "3000:3000"

.env Template

.env

1# Create server.js with SSE endpoints

Usage Notes

1Docs: https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events
2Development server at http://localhost:3000
3Create server.js with res.setHeader('Content-Type', 'text/event-stream')
4Browser: const es = new EventSource('/events'); es.onmessage = ...
5Simpler than WebSocket for one-way server-to-client streaming
6Auto-reconnection and event IDs built into protocol

Quick Start

terminal

1# 1. Create the compose file
2cat > docker-compose.yml << 'EOF'
3services:
4  sse-server:
5    image: node:20-alpine
6    container_name: sse-server
7    restart: unless-stopped
8    working_dir: /app
9    command: node server.js
10    volumes:
11      - ./app:/app
12    ports:
13      - "3000:3000"
14EOF
15
16# 2. Create the .env file
17cat > .env << 'EOF'
18# Create server.js with SSE endpoints
19EOF
20
21# 3. Start the services
22docker compose up -d
23
24# 4. View logs
25docker compose logs -f

One-Liner

Run this command to download and set up the recipe in one step:

terminal

1curl -fsSL https://docker.recipes/api/recipes/sse-server/run | bash

Troubleshooting

EventSource connection immediately closes: Ensure Content-Type header is set to 'text/event-stream' and Connection header is 'keep-alive'
Browser shows 'net::ERR_INCOMPLETE_CHUNKED_ENCODING': Remove Content-Length header and use Transfer-Encoding: chunked for streaming responses
Events not reaching client after server restart: Implement proper event ID tracking and handle last-event-id header in reconnection requests
High memory usage with many clients: Implement proper stream cleanup and remove event listeners when clients disconnect
CORS errors in browser console: Add appropriate Access-Control-Allow-Origin headers for cross-domain EventSource connections
Container exits immediately: Verify server.js exists in ./app directory and contains valid Node.js code with proper event loop handling

Community Notes

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Includes docker-compose.yml, .env template, README, and license

Components

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