ngx-socket-io

Socket.IO module for Angular

Install

npm install ngx-socket-io

Important:

Make sure you're using the proper corresponding version of socket.io on the server.

Package Version	Socket-io Server Version	Angular version	Notes
v3.4.0	v2.2.0
v4.1.0	v4.0.0	12.x
v4.2.0	v4.0.0	13.x
v4.3.0	v4.5.1	14.x
v4.4.0	v4.5.1	15.x
v4.5.0	v4.5.1	16.x
v4.6.1	v4.7.2	17.x
v4.7.0	v4.7.2	18.x
v4.8.1	v4.8.1	19.x
v4.9.0	v4.8.1	20.x
v4.9.1	v4.8.1	20.x	Zoneless

How to use

Import and configure SocketIoModule for NgModule based applications

import { SocketIoModule, SocketIoConfig } from 'ngx-socket-io';

const config: SocketIoConfig = { url: 'http://localhost:8988', options: {} };

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule, SocketIoModule.forRoot(config)],
  providers: [],
  bootstrap: [AppComponent],
})
export class AppModule {}

We need to configure SocketIoModule module using the object config of type SocketIoConfig, this object accepts two optional properties they are the same used here io(url[, options]).

Now we pass the configuration to the static method forRoot of SocketIoModule

Import and configure SocketIoModule for standalone based applications

In app.config.ts use the following:

import { ApplicationConfig } from '@angular/core';
import { SocketIoModule, SocketIoConfig, provideSocketIo } from 'ngx-socket-io';

const config: SocketIoConfig = { url: 'http://localhost:8988', options: {} };

export const appConfig: ApplicationConfig = {
  providers: [provideSocketIo(config)],
};

In standalone applications, there is no AppModule to import SocketIoModule. Instead, we use provideSocketIo(config) directly in the providers' configuration. The usage of the socket instance remains the same as in an NgModule-based application.

Using your socket Instance

The SocketIoModule provides now a configured Socket service that can be injected anywhere inside the AppModule.

import { Injectable } from '@angular/core';
import { Socket } from 'ngx-socket-io';
import { map } from 'rxjs/operators';

@Injectable()
export class ChatService {
  constructor(private socket: Socket) {}

  sendMessage(msg: string) {
    this.socket.emit('message', msg);
  }
  getMessage() {
    return this.socket.fromEvent('message').pipe(map(data => data.msg));
  }
}

Using multiple sockets with different end points

In this case we do not configure the SocketIoModule directly using forRoot. What we have to do is: extend the Socket service, and call super() with the SocketIoConfig object type (passing url & options if any).

import { Injectable, NgModule } from '@angular/core';
import { Socket } from 'ngx-socket-io';

@Injectable()
export class SocketOne extends Socket {
  constructor() {
    super({ url: 'http://url_one:portOne', options: {} });
  }
}

@Injectable()
export class SocketTwo extends Socket {
  constructor() {
    super({ url: 'http://url_two:portTwo', options: {} });
  }
}

@NgModule({
  declarations: [
    //components
  ],
  imports: [
    SocketIoModule,
    //...
  ],
  providers: [SocketOne, SocketTwo],
  bootstrap: [
    /** AppComponent **/
  ],
})
export class AppModule {}

Now you can inject SocketOne, SocketTwo in any other services and / or components.

Zoneless Implementation

Starting from version 4.9.1, ngx-socket-io no longer depends on zone.js. This means you need to manually trigger Angular's change detection when using this library in a zoneless environment.

Example Usage Here’s an example of how to use ngx-socket-io in a zoneless Angular application:

import { Component, ApplicationRef } from '@angular/core';
import { WrappedSocket } from 'ngx-socket-io';

@Component({
  selector: 'app-root',
  template: `
    <div>
      <h1>Socket.IO Example</h1>
      <p>Message: {{ message }}</p>
    </div>
  `,
})
export class AppComponent {
  message: string = '';

  constructor(private socket: WrappedSocket, private appRef: ApplicationRef) {
    // Listen to events
    this.socket.fromEvent<string>('message').subscribe((data) => {
      this.message = data;
      this.appRef.tick(); // Manually trigger change detection
    });

    // Emit events
    this.socket.emit('message', 'Hello from Angular!');
  }
}

Configuration

To configure the SocketIoModule, use the forRoot method or the provideSocketIo function:

Using forRoot

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { SocketIoModule, SocketIoConfig } from 'ngx-socket-io';

const config: SocketIoConfig = {
  url: 'https://your-websocket-server',
  options: {
    transports: ['websocket'],
  },
};

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule, SocketIoModule.forRoot(config)],
  bootstrap: [AppComponent],
})
export class AppModule {}

Using provideSocketIo

import { bootstrapApplication } from '@angular/platform-browser';
import { provideSocketIo, SocketIoConfig } from 'ngx-socket-io';

const config: SocketIoConfig = {
  url: 'https://your-websocket-server',
  options: {
    transports: ['websocket'],
  },
};

bootstrapApplication(AppComponent, {
  providers: [provideSocketIo(config)],
});

Notes

• Manual Change Detection: Since zone.js is no longer required, you must manually trigger Angular's change detection using ApplicationRef.tick() or NgZone.run() when handling WebSocket events.

• Compatibility: Ensure your application is compatible with Angular 20+ and socket.io-client v4.x.

Typings

Two typing approaches are supported: the Socket.IO Typing Pattern and the Event Payload Inline Typing.

Socket.IO Types

The Socket.IO types pattern is supported by both ngx-socket-io extended and native wrapped funcions.

Example using the following types:

interface ListenEvents {
  withAck: (callback: (n: number) => void) => void;
  fromEventSig: (onlyOneArg: FromEventSupportsOnlyOneArg) => void;
}

interface EmitEvents {
  noArg: () => void;
  basicEmit: (a: number, b: string, c: CustomObject) => void;
}

interface CustomObject {
  name: string;
  age: number;
}

interface FromEventSupportsOnlyOneArg {
  a: number;
  b: string;
  c: CustomObject;
}

To use with the default ngx-socket-io instance, simply add the types to the injected field using one of the following methods:

• constructor(private socket: Socket<ListenEvents, EmitEvents>) {}
• private socket: Socket<ListenEvents, EmitEvents> = inject(Socket)
• private socket = inject<Socket<ListenEvents, EmitEvents>>(Socket)

To use with an extension, simply specify in the class definition:

...
export class SocketOne extends Socket<ListenEvents, EmitEvents> {
...

When using, all types will be inferred automatically.

import { Component } from '@angular/core';
import { takeUntilDestroyed } from '@angular/core/rxjs-interop';
import { Socket } from 'ngx-socket-io';

@Component({
  selector: 'app-root',
  template: `
    <button (click)="noArg()">No Arg</button>
    <button (click)="basicEmit()">Basic Emit</button>
  `,
})
export class App {

  fromEventArg?: FromEventSupportsOnlyOneArg;

  constructor(
    private socket: Socket<ListenEvents, EmitEvents>
  ) {

    // Infer arg to the FromEventSupportsOnlyOneArg type.
    this.socket.fromEvent('fromEventSig')
      .pipe(takeUntilDestroyed())
      .subscribe(arg => this.fromEventArg = arg);

    // Infers the callback for a function that takes an argument of type number.
    this.socket.fromEvent('withAck')
      .pipe(takeUntilDestroyed())
      .subscribe(callback => callback(Math.random()));
  }

  noArg() {
    // Type error if any more arguments are added.
    this.socket.emit('noArg');
  }

  basicEmit() {
    // Type error if any of the arguments does not match the sequence (number, string, CustomObject) defined in the EmitEvents interface.
    this.socket.emit('basicEmit', 4.9, 'lib', { name: 'ngx', age: 8 });
  }
}

Event Payload Inline Types

Inline typing does not restrict or validate the event names supported by the socket, but it is useful for inferring the types of the parameters used by each event.

For this usage, a type variable must be specified in each socket method call. Example using the types defined previously:

export class App {

  fromEventArg?: FromEventSupportsOnlyOneArg;

  constructor(
    private socket: Socket
  ) {

    // this.socket.fromEvent return a Observable<FromEventSupportsOnlyOneArg>
    this.socket.fromEvent<FromEventSupportsOnlyOneArg>('fromEventSig')
      .pipe(takeUntilDestroyed())
      .subscribe(arg => this.fromEventArg = arg);

    this.socket.fromEvent<(n: number) => void>('withAck')
      .pipe(takeUntilDestroyed())
      .subscribe(callback => callback(Math.random()));
  }

  noArg() {
    this.socket.emit<[]>('noArg');
  }

  basicEmit() {
    // When emitting events, the parameter types must be informed within an array.
    this.socket.emit<
      [number, string, CustomObject]
      >('basicEmit', 4.9, 'lib', { name: 'ngx', age: 8 });
  }
}

API

Most of the functionalities here you are already familiar with.

The only addition is the fromEvent method, which returns an Observable that you can subscribe to.

socket.of(namespace: string)

Takes a namespace and returns an instance based on the current config and the given namespace, that is added to the end of the current url. See Namespaces - Client Initialization. Instances are reused based on the namespace.

socket.on(eventName: string, callback: Function)

Takes an event name and callback. Works the same as in Socket.IO.

socket.removeListener(eventName: string, callback?: Function)

Takes an event name and callback. Works the same as in Socket.IO.

socket.removeAllListeners(eventName?: string)

Takes an event name. Works the same as in Socket.IO.

socket.emit(eventName:string, ...args: any[])

Sends a message to the server. Works the same as in Socket.IO.

socket.fromEvent<T>(eventName: string): Observable<T>

Takes an event name and returns an Observable that you can subscribe to.

socket.fromOneTimeEvent<T>(eventName: string): Promise<T>

Creates a Promise for a one-time event.

You should keep a reference to the Observable subscription and unsubscribe when you're done with it. This prevents memory leaks as the event listener attached will be removed (using socket.removeListener) ONLY and when/if you unsubscribe.

If you have multiple subscriptions to an Observable only the last unsubscription will remove the listener.

Know Issue

For error TS2345 you need to add this to your tsconfig.json.

{
  ...
  "compilerOptions": {
    ...
    "paths": {
      "rxjs": ["node_modules/rxjs"]
    }
  },
}

Related projects

• bougarfaoui/ng-socket-io - Socket.IO module for Angular

LICENSE

MIT