How do you implement real-time features in your web app?

1 What are real-time features?

Real-time features are web app functionalities that allow users to receive and send data without refreshing the page or waiting for a response from the server. For example, in a chat app, users can see new messages as soon as they are sent by other users, and they can also send their own messages instantly. Real-time features can also involve updating data based on events or triggers, such as showing the latest stock prices, weather updates, or notifications.

2 How do real-time features work?

Real-time features work by establishing a persistent and bidirectional connection between the client (the browser) and the server (the web application). This connection allows the server to push data to the client whenever there is a change or an update, and the client to send data to the server whenever there is an input or an action. There are different ways to create this connection, such as using WebSockets, Server-Sent Events, or HTTP long polling.

3 What are WebSockets?

WebSockets are a protocol that enables full-duplex communication between the client and the server over a single TCP connection. This means that both the client and the server can send and receive data at any time, without the need for multiple HTTP requests and responses. WebSockets are widely supported by modern browsers and web servers, and they offer high performance and low latency for real-time features. To use WebSockets, you need to implement a WebSocket server that can handle the connection and the data exchange, and a WebSocket client that can connect to the server and send and receive messages. For example, in Node.js, you can use the ws module to create a WebSocket server and the WebSocket API to create a WebSocket client.

4 What are Server-Sent Events?

Server-Sent Events (SSE) are a technique that allows the server to send data to the client over an HTTP connection. Unlike WebSockets, SSE only support one-way communication from the server to the client, and they use the standard HTTP protocol. This means that they are easier to implement and more compatible with existing web infrastructure, such as proxies and firewalls. However, they also have some limitations, such as not being able to send binary data or custom headers. To use SSE, you need to create an event source on the client side that can listen to the data sent by the server, and a stream on the server side that can send data to the client using a specific content type and format. For example, in Node.js, you can use the EventSource API to create an event source and the res.write method to send data.

5 What is HTTP long polling?

HTTP long polling is a technique that simulates a real-time connection by using repeated HTTP requests and responses. The idea is that the client sends a request to the server, and the server keeps the connection open until there is data to send back to the client. Then, the client receives the response and sends another request immediately, creating a loop. This way, the client can receive data from the server as soon as it is available, without having to refresh the page or wait for a fixed interval. However, this technique also has some drawbacks, such as consuming more resources on the server and the client, and being prone to errors and timeouts. To use HTTP long polling, you need to create a function on the client side that can send requests and handle responses, and a function on the server side that can delay the response until there is data to send or a timeout occurs. For example, in Node.js, you can use the XMLHttpRequest API to send requests and the setTimeout function to delay the response.

6 How do you choose the best technology for your web app?

When deciding which technology to use for real-time features, there is no definitive answer as different technologies have their own advantages and disadvantages. Factors to consider include the level of interactivity and complexity of your features; the scalability and performance of your web app; and the availability and compatibility of libraries and frameworks. For example, WebSockets may be best for bidirectional and full-duplex communication, while SSE may be sufficient for one-way and simple communication. HTTP long polling may be the only option for supporting older browsers or legacy systems. In terms of scalability, WebSockets may offer the best performance and efficiency, but they require more resources and configuration on the server side, while SSE and HTTP long polling may be more scalable and compatible but have higher latency and bandwidth consumption. Lastly, depending on the language and platform you use for your web app, you may find more or less support for different technologies; Node.js has many modules and frameworks that facilitate the use of WebSockets, SSE, and HTTP long polling.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?