Angular RxJS WebSocket Example: A Comprehensive Guide

Angular is one of the most popular frameworks for building web applications. It provides a lot of tools and features that make it easy to develop complex applications. RxJS is a library for reactive programming that provides a lot of tools and features for managing asynchronous data streams. WebSockets are a protocol that enables real-time communication between a client and a server. In this article, we will explore how to use Angular, RxJS, and WebSockets to build a real-time application.

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What is Reactive Programming?

Reactive programming is a programming paradigm that is based on the idea of asynchronous data streams. In traditional programming, data is processed synchronously, which means that the program waits for each operation to complete before moving on to the next one. In reactive programming, data is processed asynchronously, which means that the program can continue to operate while waiting for data to arrive.

RxJS is a library for reactive programming that provides a lot of tools and features for managing asynchronous data streams. RxJS is based on the concept of Observables, which are objects that represent a stream of data. Observables can be used to represent any kind of asynchronous data source, such as events, callbacks, or HTTP requests.

What are WebSockets?

WebSockets are a protocol that enables real-time communication between a client and a server. WebSockets provide a persistent connection between the client and the server, which means that data can be sent and received in real-time without the need for repeated HTTP requests. WebSockets are ideal for applications that require real-time updates, such as chat applications, online gaming, or financial trading.

Setting up the Angular Project

The first step in building our real-time application is to set up the Angular project. We will use the Angular CLI to create a new project. Open a terminal window and run the following command:

ng new angular-websocket-example

This will create a new Angular project called “angular-websocket-example”. Once the project is created, navigate to the project directory:

cd angular-websocket-example

Next, we will install the RxJS library:

npm install rxjs

Finally, we will install the WebSocket library:

npm install websocket

Creating the WebSocket Service

The next step is to create a WebSocket service that will handle the communication between the client and the server. In Angular, services are used to encapsulate functionality that can be shared across multiple components.

Create a new file called “websocket.service.ts” in the “app” directory:

import { Injectable } from ‘@angular/core’;
import { Observable } from ‘rxjs’;
import * as Rx from ‘rxjs’;
import { webSocket } from ‘rxjs/webSocket’;
@Injectable()
export class WebSocketService {‘{‘}
private subject: Rx.Subject{‘<'}MessageEvent{'>‘};
public connect(url): Rx.Subject{‘<'}MessageEvent{'>‘} {‘{‘}
if (!this.subject) {‘{‘}
this.subject = this.create(url);
}
return this.subject;
}
private create(url): Rx.Subject{‘<'}MessageEvent{'>‘} {‘{‘}
let ws = new WebSocket(url);
let observable = Rx.Observable.create((obs: Rx.Observer{‘<'}MessageEvent{'>‘}) => {‘{‘}
ws.onmessage = obs.next.bind(obs);
ws.onerror = obs.error.bind(obs);
ws.onclose = obs.complete.bind(obs);
return ws.close.bind(ws);
})
let observer = {‘{‘}
next: (data: Object) => {‘{‘}
if (ws.readyState === WebSocket.OPEN) {‘{‘}
ws.send(JSON.stringify(data));
}
}
}
return webSocket({‘{‘}
url: url,
WebSocketCtor: () => ws,
openObserver: {‘{‘}
next: (event: Event) => {‘{‘}
ws.send(JSON.stringify({‘{‘}
type: ‘subscribe’,
channel: ‘ticker’,
symbol: ‘BTCUSD’
}));
}
},
closeObserver: {‘{‘}
next: () => {‘{‘}
this.subject = null;
}
}
}).multiplex(() => observable, () => observer);
}
{‘}’}

The WebSocket service is a class that provides a “connect” method that takes a URL as an argument and returns an Observable that represents the WebSocket connection. The “create” method is a private method that creates a new WebSocket connection and returns an Observable that represents the incoming messages. The “observer” object is used to send messages to the server.

Creating the Component

The next step is to create a component that will use the WebSocket service to display real-time data. In Angular, components are used to represent parts of the user interface.

Create a new file called “websocket.component.ts” in the “app” directory:

import {‘{‘} Component, OnInit {‘}’} from ‘@angular/core’;
import { WebSocketService } from ‘./websocket.service’;
@Component({‘{‘}
selector: ‘app-websocket’,
templateUrl: ‘./websocket.component.html’,
styleUrls: [‘./websocket.component.css’]
{‘}’})
export class WebSocketComponent implements OnInit {‘{‘}
constructor(private webSocketService: WebSocketService) {‘{}’}
ngOnInit() {‘{‘}
this.webSocketService.connect(‘wss://api.bitfinex.com/ws/2’).subscribe(message => {‘{‘}
console.log(message);
});
}
{‘}’}

The WebSocket component is a class that uses the WebSocket service to connect to a WebSocket server and display real-time data. The “ngOnInit” method is called when the component is initialized and establishes a connection to the WebSocket server using the “connect” method of the WebSocket service. The “subscribe” method is used to listen for incoming messages and display them in the console.

Displaying the Data

The final step is to display the real-time data in the user interface. We will use the Angular template syntax to bind the data to the HTML elements.

Create a new file called “websocket.component.html” in the “app” directory:

{{ message }}

This template displays the “message” variable, which will be set to the incoming messages from the WebSocket server.

Conclusion

In this tutorial, we have explored how to use Angular, RxJS, and WebSockets to build a real-time application. We have created a WebSocket service that handles the communication between the client and the server, a component that uses the WebSocket service to display real-time data, and a template that binds the data to the HTML elements. We hope that this tutorial has been helpful and informative. Happy coding!

FAQ

What is Angular?

Angular is a popular framework for building web applications. It provides a lot of tools and features that make it easy to develop complex applications.