What is a Real Time Web Application?

Over time, newer techniques have emerged to address these limitations, making real-time updates seamless and efficient. Let’s explore these approaches:

AJAX Polling

AJAX polling uses JavaScript to periodically send HTTP requests to the server to check for updates. The server responds with either new data or an empty response if no updates are available. While effective, AJAX polling is resource-intensive. Each request sets up a new TCP connection, increasing overhead and server load. For example, 1,000 clients polling every five seconds would generate 12,000 requests per minute, straining server resources.

Long Polling

Long polling improves upon AJAX polling by allowing the server to hold the client’s request open until updated data is available. The server sends the response when ready, and the client immediately sends a new request to maintain the connection.

Although more efficient than AJAX polling, long polling still relies on full HTTP requests for each update. It reduces the frequency of empty responses but can be challenging for servers to manage due to the need for multiple open connections.

WebSockets

WebSockets are the gold standard for real-time applications, enabling bidirectional communication between the client and server. After an initial HTTP handshake, the protocol switches to a persistent, full-duplex connection over a single TCP connection. This allows both the client and server to send messages independently and in real-time.

While WebSockets are efficient and fast, they require an application stack capable of handling long-lived connections. They also work outside traditional HTTP, which can complicate deployment in environments with proxies or specific security configurations. Developers need to define custom protocols for communication, adding complexity.

Server-Sent Events (SSE)

Server-Sent Events offer a simpler alternative to WebSockets for unidirectional communication. The client initiates a request, and the server sends updates as they become available, keeping the connection open indefinitely.

SSE is ideal for scenarios where the server primarily sends updates to the client, such as live news feeds or stock tickers. However, it is limited to unidirectional communication, making it unsuitable for applications requiring frequent client-to-server interaction.