<a href="https://javascript.info/long-polling">Long Polling</a>, <a href="https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events">Server-Sent Events (SSE)</a>, and <a href="https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API">WebSocket</a> are three different technologies used for real-time communication between a client and a server.
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<h2>Long Polling:</h2>
Long Polling is suitable for scenarios where you need near-real-time updates but don't require extremely low latency. It's often used when WebSocket support is not available on the client-side or server-side.
<pre class="shiki github-dark shaku"><code>function longPoll() { fetch('/longpoll-endpoint') .then(response =&gt; { // Handle the response and initiate another long poll longPoll(); }) .catch(error =&gt; { // Handle errors });}// Start the long polling processlongPoll();</code></pre>
Pros: It's relatively easy to implement on both the client and server. Works in environments without WebSocket support.
Cons: It can consume more server resources and bandwidth compared to other techniques. Long Polling introduces some latency as clients have to wait for the next response.
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<h2>Server-Sent Events (SSE):</h2>
SSE is suitable for scenarios where you need server-to-client communication, but the client is primarily interested in receiving updates from the server. It's useful for applications like news feeds or live score updates.
<pre class="shiki github-dark shaku"><code>const eventSource = new EventSource('/sse-endpoint');eventSource.onmessage = event =&gt; { // Handle the event data console.log(event.data);};eventSource.onerror = error =&gt; { // Handle errors and reconnect if needed};</code></pre>
Pros: SSE is easy to set up and use, especially on the client-side. It's more efficient than Long Polling in terms of server resources and bandwidth. Also, SSE automatically attempts to reconnect if the connection is lost.
Cons: SSE is a one-way communication channel (server to client). If you need bidirectional communication, you'll need to complement it with another technology. It is well-supported in modern browsers but may not work in older versions.
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<h2>WebSocket:</h2>
WebSocket is suitable for real-time bidirectional communication where low latency and high interactivity are crucial, such as online gaming, chat applications, or collaborative tools.
<pre class="shiki github-dark shaku"><code>const socket = new WebSocket('ws://example.com/socket-endpoint');socket.onopen = event =&gt; { // Connection established, send/receive data here};socket.onmessage = event =&gt; { // Handle messages from the server console.log(event.data);};socket.onerror = error =&gt; { // Handle errors};socket.onclose = event =&gt; { // Handle the connection closure and attempt to reconnect if needed};</code></pre>
Pros: WebSocket provides low-latency, full-duplex communication, making it ideal for interactive applications. It allows data to be sent from both the client and server simultaneously. It's more efficient than Long Polling and SSE in terms of both bandwidth and server resources.
Cons: Implementing WebSocket can be more complex than Long Polling or SSE, especially on the server-side. Also, some network setups may block WebSocket connections, requiring additional configuration.
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Long Polling is suitable for basic real-time updates when WebSocket is not available, SSE is great for one-way server-to-client communication, and WebSocket is the best choice for low-latency, bidirectional communication in interactive applications.

Long Polling vs Sever-Sent Event vs WebSocket explained

Long Polling, Sever-Sent Events and WebSocket are 3 approaches to real-time application. Depending on where it is used, each of them could be the bett…