TypeScript real-time applications: developing chat using WebSocket, Node, and Angular

I recently created a simple chat using only TypeScript. The main goal of this project was to write an application demonstrating the use of this language on both the client and the server. The client part of the chat is based on the latest version of Angular. The server is based on Node.js. The interaction between them is organized using the WebSocket protocol.

In this article you will learn how to create the chat in question from scratch. Here, by the way, looks like working with him.

TypeScript Chat

About real-time applications

According to this definition from Wikipedia, a real-time application allows interested entities to receive information immediately after it has been published, without the need for a periodic survey of the source of information. Thus, this kind of application should give users the feeling that certain actions occur instantly, without delay.

WebSocket Protocol

WebSocket is a protocol that allows you to organize a bi-directional data channel. In our case, this means that the browser and the web server can communicate in real time, sending messages to each other when there is an open connection between them.


WebSocket Communication

Application structure

We will place the code related to the client and server parts of the application in separate folders. The structure of the finished application is shown below. We will consider the details below when we talk about the key files of our project.

server/
|- src/
|- package.json
|- tsconfig.json
|- gulpfile.js
client/
|- src/
|- package.json
|- tsconfig.json
|- .angular-cli.json

Choosing a WebSocket Implementation

Since the WebSocket protocol is a specification , several practical implementations can be found . Here you can use JavaScript , TypeScript, or any other programming language.

In this case, we will use the Socket.IO library . This is one of the fastest and most reliable libraries that implements real-time data exchange capabilities.

Why use TypeScript on a server?

TypeScript offers the programmer great features , the development team keeps the language up to date. In addition, the use of typing can reduce the number of errors in the code, compared to using regular JS. For me, these reasons are quite enough for using TS on the server.

Server Application Initialization

Create a file package.jsonand install the following dependencies:

npm install --save express socket.io @types/express @types/socket.io

In addition, you will need to establish some development dependencies in order to integrate into the project gulpand typescript, all this will be useful to us during the creation and assembly of the finished project:

npm install --save-dev typescript gulp gulp-typescript

TypeScript Compiler Setup

Create a file tsconfig.jsonand put the following into it:

{
  "files": [
    "src/*.ts",
    "src/model/*.ts"
  ],
  "compilerOptions": {
    "target": "es5"
  }
}

Data Model Description

Using the capabilities of static typing, we will create a small data model:

export class User {
    constructor(private name: string) {}
}
export class Message {
    constructor(private from: User, private content: string) {}
}
export class ChatMessage extends Message{
    constructor(from: User, content: string) {
        super(from, content);
    }
}

Take a look at the directory structure server/src:

server/
|- src/
   |- model/
      |- message.model.ts
      |- user.model.ts
   |- index.ts
   |- server.ts
|- package.json
|- tsconfig.json
|- gulpfile.js

Chat server implementation

The main files in the directory serverare index.tsand chat-server.ts. The first allows you to create and export the application ChatServer, while the second contains the express and Socket.IO configurations :

Here is the file code index.js:

import { ChatServer } from './chat-server';
let app = new ChatServer().getApp();
export { app };

Here is the file chat-server.ts:

import { createServer, Server } from 'http';
import * as express from 'express';
import * as socketIo from 'socket.io';
import { Message } from './model';
export class ChatServer {
    public static readonly PORT:number = 8080;
    private app: express.Application;
    private server: Server;
    private io: SocketIO.Server;
    private port: string | number;
    constructor() {
        this.createApp();
        this.config();
        this.createServer();
        this.sockets();
        this.listen();
    }
    private createApp(): void {
        this.app = express();
    }
    private createServer(): void {
        this.server = createServer(this.app);
    }
    private config(): void {
        this.port = process.env.PORT || ChatServer.PORT;
    }
    private sockets(): void {
        this.io = socketIo(this.server);
    }
    private listen(): void {
        this.server.listen(this.port, () => {
            console.log('Running server on port %s', this.port);
        });
        this.io.on('connect', (socket: any) => {
            console.log('Connected client on port %s.', this.port);
            socket.on('message', (m: Message) => {
                console.log('[server](message): %s', JSON.stringify(m));
                this.io.emit('message', m);
            });
            socket.on('disconnect', () => {
                console.log('Client disconnected');
            });
        });
    }
    public getApp(): express.Application {
        return this.app;
    }
}

Server Classes

The code above gives the following classes and the relationships between them:


Server Class Diagram

Build and start the server

In order to get the JavaScript files needed by the V8 engine on which Node.js is based, add the task buildto the file gulpfile.js:

var gulp = require("gulp");
var ts = require("gulp-typescript");
var tsProject = ts.createProject("tsconfig.json");
gulp.task("build", function () {
    return tsProject.src()
        .pipe(tsProject())
        .js.pipe(gulp.dest("./dist"));
});

As you can see, the output of the build process (JS files) will be located in the directory dist. In order to complete the assembly, you will need the following command:

gulp build

Now, in order to start the server, you need to use the following command:

node dist/index.js

Chat client development

Create a folder for the client using the Angular CLI :

ng new typescript-chat-client --routing --prefix tcc --skip-install

Install the project dependencies. Here you can execute the command npm install, but I prefer to use Yarn in this step :

cd typescript-chat-client
yarn install

Adding an Angular Material Component Set to a Project

To take advantage of the Angular Material component set in a project created using the Angular CLI, take a look at the latest manual on material.angular.io and act on it.

In accordance with the recommendations on the structure of Angular projects, we will create modules sharedand material:

client/
|- src/
   |- app/
      |- chat/
      |- shared/
         |- material/
            |- material.module.ts
         |- shared.module.ts
      |-app.module.ts

You can do this from the command line:

ng generate module shared --module app
ng generate module shared/material --module shared

In order to evaluate the relationship between these modules, analyze the files app.module.tsand shared.module.ts.

Connect express and Socket.IO

Now you need to connect the modules to our client application expressand socket.io:

npm install express socket.io --save

Chat Modules and Components

Before creating chat components, create a new module:

ng generate module chat --module app

Now add the component to this module:

ng generate component chat --module chat

In order to use web sockets and our own models, create another folder shared. This time inside the directory chat:

ng generate service chat/shared/services/socket --module chat
ng generate class chat/shared/model/user
ng generate class chat/shared/model/message

The result should be the following structure:

client/
|- src/
   |- app/
      |- chat/
         |- shared/
           |- model/
              |- user.ts
              |- message.ts
           |- services/
              |- socket.service.ts
      |- shared/
      |-app.module.ts

Observed objects and web sockets

Since our Angular application supports RxJS, you can use observable objects to work with Socket.IO events. Therefore, the file socket.services.tswill look like this:

import { Injectable } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import { Observer } from 'rxjs/Observer';
import { Message } from '../model/message';
import { Event } from '../model/event';
import * as socketIo from 'socket.io-client';
const SERVER_URL = 'http://localhost:8080';
@Injectable()
export class SocketService {
    private socket;
    public initSocket(): void {
        this.socket = socketIo(SERVER_URL);
    }
    public send(message: Message): void {
        this.socket.emit('message', message);
    }
    public onMessage(): Observable {
        return new Observable(observer => {
            this.socket.on('message', (data: Message) => observer.next(data));
        });
    }
    public onEvent(event: Event): Observable {
        return new Observable(observer => {
            this.socket.on(event, () => observer.next());
        });
    }
}

Now we are ready to respond to messages from the server, so let's look at the file chat.component.ts(here the code regarding Material and user interface events is omitted):

import { Component, OnInit } from '@angular/core';
import { Action } from './shared/model/action';
import { Event } from './shared/model/event';
import { Message } from './shared/model/message';
import { User } from './shared/model/user';
import { SocketService } from './shared/services/socket.service';
@Component({
  selector: 'tcc-chat',
  templateUrl: './chat.component.html',
  styleUrls: ['./chat.component.css']
})
export class ChatComponent implements OnInit {
  action = Action;
  user: User;
  messages: Message[] = [];
  messageContent: string;
  ioConnection: any;
  constructor(private socketService: SocketService) { }
  ngOnInit(): void {
    this.initIoConnection();
  }
  private initIoConnection(): void {
    this.socketService.initSocket();
    this.ioConnection = this.socketService.onMessage()
      .subscribe((message: Message) => {
        this.messages.push(message);
      });
    this.socketService.onEvent(Event.CONNECT)
      .subscribe(() => {
        console.log('connected');
      });
    this.socketService.onEvent(Event.DISCONNECT)
      .subscribe(() => {
        console.log('disconnected');
      });
  }
  public sendMessage(message: string): void {
    if (!message) {
      return;
    }
    this.socketService.send({
      from: this.user,
      content: message
    });
    this.messageContent = null;
  }
  public sendNotification(params: any, action: Action): void {
    let message: Message;
    if (action === Action.JOINED) {
      message = {
        from: this.user,
        action: action
      }
    } else if (action === Action.RENAME) {
      message = {
        action: action,
        content: {
          username: this.user.name,
          previousUsername: params.previousUsername
        }
      };
    }
    this.socketService.send(message);
  }
}

As soon as it is ChatComponentinitialized, the component subscribes to monitored objects SocketServicein order to receive connection-related events or incoming messages.

Functions sendMessageand sendNotificationwill send, respectively, messages and notifications through the same service. Notifications are used to notify the system that a new user has joined the chat and to rename the chat participants.

Summary

From this material, you learned how to use a TypeScript to write a real-time application - a chat in which TS is used both on the client and on the server, and in which technologies such as WebSockets, Node.js and Angular are involved. The source code of the project can be found here . And here is a working chat (open a couple of tabs with this page in your browser in order to experience it).

Dear readers! Do you use TypeScript to develop server applications?