Real Time JavaScript Web Apps with WebSockets, SSE, and WebTransport

UpdatedMarch 13, 2025

•2 min read

Real Time JavaScript Web Apps with WebSockets, SSE, and WebTransport

Senior Software Engineer specialising in cloud architecture, distributed systems, and modern .NET development, with over two decades of experience designing and delivering enterprise platforms in financial, insurance, and high-scale commercial environments. My focus is on building systems that are reliable, scalable, and maintainable over the long term. I’ve led modernisation initiatives moving legacy platforms to cloud-native Azure architectures, designed high-throughput streaming solutions to eliminate performance bottlenecks, and implemented secure microservices environments using container-based deployment models and event-driven integration patterns. From an architecture perspective, I have strong practical experience applying approaches such as Vertical Slice Architecture, Domain-Driven Design, Clean Architecture, and Hexagonal Architecture. I’m particularly interested in modular system design that balances delivery speed with long-term sustainability, and I enjoy solving complex problems involving distributed workflows, performance optimisation, and system reliability. I enjoy mentoring engineers, contributing to architectural decisions, and helping teams simplify complex systems into clear, maintainable designs. I’m always open to connecting with other engineers, architects, and technology leaders working on modern cloud and distributed system challenges.

Building real time web applications requires efficient communication between the client and server. Whether updating a live dashboard, enabling instant messaging, or synchronising data across multiple users, the right technology makes a significant difference. Traditional request response models introduce unnecessary delays, which can be avoided using persistent connections that keep data flowing without repeated polling.

WebSockets provide full duplex communication, allowing data to move freely between client and server without waiting for a request. Once a connection is established, messages can be sent in either direction instantly. This makes WebSockets an ideal choice for chat applications, multiplayer gaming, and collaborative tools. A typical implementation involves setting up a WebSocket server and handling messages asynchronously.

const ws = new WebSocket('wss://example.com/socket');
ws.onopen = () => {
    ws.send('Hello server!');
};
ws.onmessage = (event) => {
    console.log('Message from server:', event.data);
};

For scenarios where a one way data stream is sufficient, Server Sent Events (SSE) offer a lightweight alternative. The client establishes a persistent connection and listens for updates, but unlike WebSockets, communication flows in one direction. This is particularly useful for stock market tickers, live news feeds, and notifications. Since SSE operates over standard HTTP, it benefits from reconnection handling and works well with load balancers.

const eventSource = new EventSource('/events');
eventSource.onmessage = (event) => {
    console.log('New event:', event.data);
};

A newer option, WebTransport, is gaining traction for scenarios demanding low latency, high performance communication. Built on top of HTTP/3, it offers a more efficient way to handle unreliable or ordered data delivery compared to WebSockets. This is particularly relevant for streaming video, online gaming, and IoT applications where reducing overhead is a priority. While WebTransport is still evolving, it provides advantages in bandwidth efficiency and security, making it a strong contender for modern real-time applications.

Choosing the right technology depends on the specific needs of the application. WebSockets excel in bidirectional interactions, SSE simplifies server-to-client updates, and WebTransport unlocks new possibilities for latency sensitive communication. As real-time functionality becomes a standard expectation in web applications, leveraging the right tool ensures a good user experience with minimal performance trade offs.