Oct 31, 2024
In today’s fast-paced digital landscape, real-time communication between clients and servers is crucial for enhancing user experience. Whether it’s live notifications, messaging, or collaborative apps, users expect updates instantly.
Three popular technologies make this possible: Server-Sent Events (SSE), WebSockets, and Long Polling. We will walk you through each, their strengths, and how to choose the right one for your application.
What is Server-Sent Events (SSE)?
Server-Sent Events (SSE) is a simple, efficient way for servers to send real-time updates to clients over HTTP. With SSE, the server can push updates to the client by keeping a single HTTP connection open, making it lightweight and resource-efficient for one-way data streams.
When to Use SSE: - Ideal for applications that need a one-way communication stream from server to client, like live news feeds, notifications, or stock prices. - Works well over HTTP and has built-in reconnection logic if the connection drops, providing reliable and low-latency updates.
What are WebSockets?
WebSockets provide a full-duplex communication channel, allowing data to flow both ways between the client and server in real-time. After an initial HTTP handshake, the protocol upgrades to a persistent WebSocket connection, enabling both parties to send data whenever needed. This bidirectional nature makes WebSockets ideal for interactive applications.
When to Use WebSockets: - Perfect for applications requiring continuous two-way interaction, such as chat applications, multiplayer games, or collaborative tools. - Although it’s more resource-intensive than SSE, WebSockets are highly efficient for applications that demand frequent and quick exchanges of data between client and server.
What is Long Polling?
Long polling is an older technique for simulating real-time updates using repeated HTTP requests. The client sends a request to the server and waits until there is new data (or a timeout). Once the server responds, the client immediately opens a new connection. Though effective, it can create more server load compared to SSE and WebSockets due to repeated HTTP connections.
When to Use Long Polling: - Best suited as a fallback when real-time updates are needed, but WebSockets or SSE are unavailable. - Reliable in restricted environments (such as certain corporate or mobile networks) where WebSockets might not be feasible.
Comparison Table: SSE, WebSockets, and Long Polling
| Feature | Server-Sent Events (SSE) | WebSockets | Long Polling |
|---|---|---|---|
| Data Direction | One-way: Server to client | Two-way: Client and server | One-way: Server to client |
| Protocol | HTTP (usually HTTP/2) | WebSocket protocol (starts with HTTP, upgrades) | HTTP |
| Connection Type | Persistent HTTP connection | Persistent, full-duplex | Multiple short-lived HTTP requests |
| Connection Handling | Automatic reconnection if interrupted | Requires custom reconnection logic | New request sent after each response or timeout |
| Efficiency | Lightweight, ideal for one-way data streams | Efficient for frequent, two-way data | Can be resource-heavy due to frequent HTTP handshakes |
| Scalability | Scales well for many clients receiving similar data | Needs careful server management for high traffic | More server load due to repeated HTTP connections |
| Reliability | Compatible with HTTP infrastructure (proxies, load balancers) | Potential issues with firewalls or proxies blocking WebSocket | Compatible with most network setups |
| Latency | Low latency, slightly slower than WebSockets | Very low latency, ideal for real-time interactions | Higher latency due to connection overhead |
| Use Cases | Live news, notifications, stock price updates | Chat apps, multiplayer games, collaborative tools | Real-time updates where WebSocket/SSE is unsupported |
Choosing the Right Technology for Real-Time Communication
Selecting the right real-time communication technology depends on the specific needs of your application. Here’s a quick guide:
- Use SSE if you only need one-way updates from the server to the client, such as notifications, news feeds, or live event updates. SSE provides a simple, reliable, and resource-efficient solution.
- Use WebSockets if you require bidirectional, continuous communication between the client and server, as in chat applications or real-time collaborative tools. WebSockets are robust for highly interactive applications where both parties frequently exchange data.
- Use Long Polling if other real-time solutions are not feasible. Although it’s less efficient, long polling is widely compatible and can simulate real-time updates effectively.
Conclusion
SSE, WebSockets, and Long Polling each have unique strengths, with different use cases that make them optimal for certain types of applications. By understanding their differences, you can pick the right tool to build responsive, engaging, and real-time applications for your users.
Ming Dao School uses 1-1 coaching and group events to help high-tech professionals grow their careers and handle career transitions.
If you like to join our upcoming mock system design interview events or other coaching programs, please contact us on LinkedIn.