JavaScript, WebSockets & How to Build Real-Time Applications

Web DevelopmentUPDATED ON October 18, 2019

WebSockets in Real Time Applications

The Why And How Of WebSockets And Real Time Applications

The era of WebSockets, as well as real-time applications (RTA), in web development is upon us. Persistent connections and broadcasting to connected clients is now part and parcel of almost every modern application. Today’s consumers expect on-demand rather than static apps. So, how do we take part by building an RTA?

What is a Real Time Application (RTA)?

If we open the Wikipedia article devoted to the real-time web, we’ll find the following description of an RTA:

An RTA enables users to receive information as soon as it is published by its authors, rather than requiring that they or their software check a source periodically for updates.” This means that all operations are happening with a small latency (usually measured in seconds) that allows users to think that everything happens in real-time. In other words, all processes are felt as immediate and current.

Here are some examples of RTAs most will be familiar with:

  • Video conference applications
  • VoIP (voice over Internet Protocol)
  • Online gaming
  • Community storage solutions
  • Certain e-commerce transactions
  • Chatting
  • IM (instant messaging)
  • IoT

How Does a Real Time Application Function?

The way an RTA functions depends mostly on realtime API mechanisms, of which there are four in total:

  • HTTP streaming
  • HTTP long-polling
  • Webhooks
  • WebSockets

Here we’d like to explain a little more about WebSockets and polling as they represent the basic operating principle of an RTA.


Here is how polling functions:

  1. There are certain time periods, after which a request is sent to the server to check for updates in the form of a vote;
  2. The server on its side looks for any updates. If there are any, it confirms it by sending an up-vote. If not, it replies with a down-vote.
  3. At the user end, if the server casts an up-vote, the system further asks for the updated data, which is then passed by the server.
  4. Once this process is over, requests are sent again to the server at the regular time intervals.

Ajax is chosen because of being lightweight and able to update parts of the page without reloading it entirely. The only issue is with the bandwidth, which is later resolved with the help of a method called long polling. According to the method, an HTTP request stays up until a new message is sent by a server.

Long Polling via Ajax

Long polling via Ajax

Today, these approaches might be still used, yet most developers tend to use other ways of achieving server-push.


If we began to talk about polling and long polling, we can’t omit such things as Comet. This is basically a neologism that describes the model of a web application. In the usual cycle of request processing, the client initiates the connection and requests the document of interest. After the data is returned, the connection is broken. In the case of Сomet, the server initiates the connection and sends a message to the client. A good example of Comet is notifications in Facebook, Twitter, chat in Gmail, etc.

The reason it’s mentioned in conjunction with polling is that Comet includes and is being realized through polling, long-polling, and even HTML5 WebSockets, which we’ll discuss further.

WebSockets in Real Time Applications

Back in 2011, the WebSockets protocol appeared. Its primary function is to provide a bi-directional communication channel. This allows a browser and a web server to interact, providing them with a two-way persistent connection, within which they can send messages back and forth while the connection is open.

The WebSockets protocol is immensely important for the responsiveness of an application, which usually has many concurrent connections and quickly changing content — a good example is a multiplayer online game.

Where Are WebSockets Used In Real Time Applications?

WebSockets is becoming increasingly more popular among Web developers nowadays, and can be implemented for the following purposes:

  • Chat applications: Video and audio conferencing applications
  • Multiplayer online gaming
  • Social feeds
  • Simultaneous file sharing

The list can be continued further with:

  • stock market monitoring
  • sports updates
  • an online broadcast, etc.

Examples are: Blockchain, Coinbase, CBIX, Slack

What Do We Need to Develop WebSockets-based RTA?

After we have got some insight into the topic, let’s define what technology pool we need for the development of an RTA on the base of WebSockets API mechanism.

Technology Pool

Your platform is

WebSockets in RTAs

Your database is

Database for Use In Real Time Applications

Your Tool For Server-Side Templating

Server-side Templating Tools For Real Time Applications

The K&C team hopes you find this article useful as your application enters the world of real-time! If you still have questions, don’t hesitate to reach out to us.

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