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Identifying the Problem

When working with websocket packages in NestJS, it is common to run into certain issues that can disrupt your development process. Two of the most common problems include:

  1. Incorrect package installation: This is usually the root cause of most issues with websocket packages in NestJS. If the package is not installed correctly, it may not function as expected or may cause other parts of your application to break.

  2. Misconfiguration of the websocket package: If the websocket package is not configured correctly, it may not be able to establish a connection with the client, which can lead to a variety of issues.

Incorrect Package Installation

An incorrect package installation can occur in several ways. You might install the wrong version of the package, or the installation might fail due to network issues. Here is an example of how to correctly install the package, a common websocket package used in NestJS:

npm install @nestjs/

In this example, we are using npm to install the @nestjs/ package. If the package is installed correctly, you should be able to import it into your application without any issues.

Misconfiguration of the Websocket Package

Once the package is installed, it needs to be configured correctly in order to function. Misconfiguration can occur if you fail to provide the necessary parameters or if you provide incorrect parameters. Here is an example of how to correctly configure the package:

import { Server, Socket } from '';
import { WebSocketGateway, WebSocketServer } from '@nestjs/websockets';

export class EventsGateway {
  server: Server;

  handleConnection(client: Socket, ...args: any[]) {
    console.log('Client connected: ',;

In this example, we are using the @WebSocketGateway and @WebSocketServer decorators from the @nestjs/websockets package to create a websocket gateway. The handleConnection method is called whenever a new client connects to the server.

Troubleshooting the Issues

If you are still encountering issues with the websocket package after ensuring that it is installed and configured correctly, there are a few additional steps you can take to troubleshoot the problem:

  1. Check the package documentation: The documentation for the package will often contain information about common issues and how to resolve them. Make sure you are following the instructions in the documentation exactly.

  2. Look for error messages: If there is an issue with the websocket package, there will likely be an error message in the console. This error message can provide valuable clues about what is causing the problem.

Example of a Common Error Message

Here is an example of a common error message you might encounter when working with websocket packages in NestJS:

Error: Cannot find module '@nestjs/'

This error message indicates that the @nestjs/ module cannot be found. This could mean that the package is not installed correctly, or that there is an issue with the way the package is being imported into your application.

Resolving the Error Message

To resolve this error message, you would first need to ensure that the @nestjs/ package is installed correctly. You can do this by running the following command in your terminal:

npm install @nestjs/

Next, you would need to ensure that the package is being imported correctly. Here is an example of how to correctly import the @nestjs/ package into your application:

import { WebSocketGateway, WebSocketServer } from '@nestjs/websockets';

In this example, we are importing the @WebSocketGateway and @WebSocketServer decorators from the @nestjs/websockets package. These decorators are used to create a websocket gateway and server, respectively.

Final Thoughts

Working with websocket packages in NestJS can be challenging, especially when you encounter issues that disrupt your development process. However, by understanding the root causes of these issues and knowing how to troubleshoot them, you can resolve these issues quickly and get back to developing your application.

Remember, the key to resolving issues with websocket packages is to ensure that the package is installed and configured correctly. Always check the package documentation and look for error messages in the console for clues about what might be causing the problem.

First of all, it’s important to understand what the Websocket package in NestJS is. It’s a module that allows real-time, two-way communication between the server and the client in a web-based application. However, when not set up properly, it can lead to various errors that can disrupt the smooth functioning of your application.

Let’s start with the most common error - WebSocket is not a constructor. This error typically occurs when the Websocket package is not imported correctly. The correct way to import the package in your NestJS application is as follows:

import { WebSocketGateway, WebSocketServer } from '@nestjs/websockets';

In the above code, @nestjs/websockets is the module that provides the Websocket functionality in NestJS. WebSocketGateway and WebSocketServer are decorators that are used to define a Websocket gateway and server respectively.

Another common error is TypeError: Cannot read property 'clients' of undefined. This happens when you’re trying to access the clients property of the server, but the server hasn’t been initialized yet. To fix this, you need to ensure that your server is initialized before you try to access its properties. Here’s how you can do it:

export class EventsGateway {

  handleConnection(client) {
    // This will be called when a client connects to the server
    console.log('Client connected:',;

  handleDisconnect(client) {
    // This will be called when a client disconnects from the server
    console.log('Client disconnected:',;

In the above code, handleConnection and handleDisconnect are event handlers that are called when a client connects to or disconnects from the server. The server property is initialized when the EventsGateway class is instantiated, so you can safely access server.clients within these methods.

Yet another error that you might encounter is Error: listen EADDRINUSE :::3001. This error means that the port you’re trying to use for your Websocket server is already in use by another process. The solution is to either stop the other process or use a different port for your Websocket server. You can specify the port for your Websocket server like this:

@WebSocketGateway(3002) // Use a different port
export class EventsGateway {
  // ...

In the above code, 3002 is the port number. You can replace it with any valid port number that is not in use.

Sometimes, you might also see an error like Error: WebSocket is not open: readyState 3 (CLOSED). This error occurs when you’re trying to send a message to a Websocket client, but the connection has already been closed. To prevent this error, you should always check the readyState of the Websocket client before sending a message. Here’s an example:

handleEvent(client, data) {
  if (client.readyState === WebSocket.OPEN) {

In the above code, WebSocket.OPEN is a constant that represents the open state of a Websocket connection. client.readyState is the current state of the client’s connection. If it’s equal to WebSocket.OPEN, it means the connection is open and you can safely send a message.

In conclusion, resolving Websocket package issues in NestJS involves understanding the errors, knowing why they occur, and applying the appropriate solutions. It’s a process that requires a good understanding of both NestJS and the Websocket protocol, but with practice and experience, you’ll be able to handle these issues with ease.

Remember, when working with Websockets in NestJS, always ensure that you’re importing the package correctly, initializing your server before accessing its properties, using a valid and available port for your server, and checking the connection state before sending messages. By following these guidelines, you’ll be able to build robust and reliable real-time applications with NestJS and Websockets.

I hope this post has been helpful in resolving your Websocket package issues in NestJS. If you have any questions or need further clarification on any of the points discussed, feel free to leave a comment below. Happy coding!

Recommended Sites

If you’re looking to resolve Websocket package issues in NestJS, the following official sites are highly recommended. These resources provide comprehensive information and are regularly updated to ensure you’re getting the most accurate and up-to-date information.

Please ensure that you check these sites regularly for updates and additional information. They are reliable sources and do not have 404 errors, providing a seamless user experience.