WebSocket guards and pipes in NestJS - Mini Project: Build & Apply

WebSocket Guards and Pipes in NestJS

📖 Scenario: You are building a simple chat server using NestJS WebSocket gateway. You want to control access and validate incoming messages.

🎯 Goal: Create a WebSocket gateway with a guard that allows only authenticated users and a pipe that validates the message format.

📋 What You'll Learn

Create a WebSocket gateway class named ChatGateway

Create a guard class named AuthGuard that implements CanActivate

Create a pipe class named MessageValidationPipe that implements PipeTransform

Apply the AuthGuard to the gateway using @UseGuards(AuthGuard)

Apply the MessageValidationPipe to the message handler method using @UsePipes(MessageValidationPipe)

The message handler method should be named handleMessage and accept a message parameter

💡 Why This Matters

🌍 Real World

WebSocket guards and pipes help secure and validate real-time communication in chat apps, games, and live updates.

💼 Career

Understanding guards and pipes in NestJS is essential for backend developers building secure and robust WebSocket APIs.

1

Create the WebSocket gateway class

Create a class named ChatGateway decorated with @WebSocketGateway(). Inside it, create a method named handleMessage that takes a parameter message of type string.

NestJS

@WebSocketGateway()
export class ChatGateway {
  // Create handleMessage method here
  // Your code here
}

Need a hint?

Use @WebSocketGateway() decorator from @nestjs/websockets and define the class and method exactly as named.

2

Create the AuthGuard class

Create a class named AuthGuard that implements CanActivate interface. Implement the canActivate method that returns true.

NestJS

@WebSocketGateway()
export class ChatGateway {
  handleMessage(message: string) {
    // message handling logic
  }
}

// Create AuthGuard class here
// Your code here

Need a hint?

Import CanActivate and ExecutionContext from @nestjs/common. Implement canActivate to always return true.

3

Create the MessageValidationPipe class

Create a class named MessageValidationPipe that implements PipeTransform. Implement the transform method that takes a value parameter and returns it unchanged.

NestJS

@WebSocketGateway()
export class ChatGateway {
  handleMessage(message: string) {
    // message handling logic
  }
}

import { CanActivate, ExecutionContext } from '@nestjs/common';

export class AuthGuard implements CanActivate {
  canActivate(context: ExecutionContext): boolean {
    return true;
  }
}

// Create MessageValidationPipe class here
// Your code here

Need a hint?

Import PipeTransform from @nestjs/common. The transform method should return the input value unchanged.

4

Apply the guard and pipe to the gateway and handler

Add the @UseGuards(AuthGuard) decorator to the ChatGateway class. Add the @UsePipes(MessageValidationPipe) decorator to the handleMessage method.

NestJS

@WebSocketGateway()
export class ChatGateway {
  handleMessage(message: string) {
    // message handling logic
  }
}

import { CanActivate, ExecutionContext, PipeTransform } from '@nestjs/common';

export class AuthGuard implements CanActivate {
  canActivate(context: ExecutionContext): boolean {
    return true;
  }
}

export class MessageValidationPipe implements PipeTransform {
  transform(value: any) {
    return value;
  }
}

// Add decorators @UseGuards and @UsePipes
// Your code here

Need a hint?

Import UseGuards and UsePipes from @nestjs/common. Decorate the class and method exactly as specified.