WebSocket gateway creation in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a WebSocket Gateway in NestJS?

A WebSocket Gateway in NestJS is a special class that handles WebSocket connections, allowing real-time communication between the server and clients.

beginner

Which decorator is used to create a WebSocket Gateway in NestJS?

The @WebSocketGateway() decorator is used to mark a class as a WebSocket Gateway in NestJS.

beginner

How do you listen for a specific WebSocket event in a NestJS Gateway?

Use the @SubscribeMessage('eventName') decorator on a method inside the Gateway class to listen for that event.

intermediate

What method signature should a message handler have in a NestJS WebSocket Gateway?

A message handler method should accept two parameters: the client socket and the data sent by the client, e.g., handleMessage(client: Socket, payload: any).

beginner

How can you send a message back to the client from a WebSocket Gateway in NestJS?

You can use the client.emit('eventName', data) method to send a message back to the connected client.

Which decorator marks a class as a WebSocket Gateway in NestJS?

A @Controller()

B @WebSocketGateway()

C @Injectable()

D @Module()

The @WebSocketGateway() decorator is specifically used to create WebSocket Gateways.

How do you listen for a WebSocket event named 'chat' in a NestJS Gateway?

A Use @SubscribeMessage('chat') on a method

B Use @OnEvent('chat') on a method

C Use @Listen('chat') on a method

D Use @WebSocketEvent('chat') on a method

The @SubscribeMessage('eventName') decorator listens for WebSocket events.

What parameters does a WebSocket message handler method usually receive?

A only client socket

B request and response objects

C only payload data

D client socket and payload data

Handlers receive the client socket and the data sent by the client.

Which method sends a message back to the client in a NestJS WebSocket Gateway?

A gateway.emit()

B client.sendMessage()

C client.emit()

D gateway.send()

client.emit() sends an event with data back to the connected client.

What is the main purpose of a WebSocket Gateway in NestJS?

A To handle real-time WebSocket communication

B To serve static files

C To manage database connections

D To handle HTTP requests

WebSocket Gateways manage real-time communication using WebSockets.

Explain how to create a basic WebSocket Gateway in NestJS and listen for a message event.

Think about decorators and message handlers.

Describe how a NestJS WebSocket Gateway handles incoming messages and sends responses.

Focus on the flow of message handling.