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Javascript NestJS Error: EADDRINUSE, Address already in use
Understanding NestJS and Its Purpose
NestJS is a progressive Node.js framework for building efficient, reliable, and scalable server-side applications. It leverages TypeScript, combining elements of OOP (Object Oriented Programming), FP (Functional Programming), and FRP (Functional Reactive Programming). NestJS is designed to provide a solid architecture out of the box, making it easier to manage and scale applications.
Identifying the Symptom: EADDRINUSE Error
When working with NestJS, you might encounter the error message: Error: EADDRINUSE, Address already in use. This error typically occurs when you attempt to start your NestJS application, and the specified port is already occupied by another process.
Understanding the EADDRINUSE Error
The EADDRINUSE error indicates that the port your application is trying to bind to is already in use. This can happen if another instance of your application is running or if another application is using the same port. Ports are unique endpoints for network communication, and only one process can listen on a specific port at a time.
Common Causes of the Error
- Another instance of the application is already running.
- Another application is using the same port.
- The application did not shut down properly, leaving the port occupied.
Steps to Resolve the EADDRINUSE Error
To resolve the EADDRINUSE error, you can follow these steps:
Step 1: Identify the Process Using the Port
First, you need to identify which process is using the port. You can do this using the following command:
lsof -i :<port_number>
Replace <port_number> with the port number your application is trying to use. This command will list the processes using that port.
Step 2: Terminate the Process
Once you have identified the process, you can terminate it using the kill command:
kill -9 <PID>
Replace <PID> with the process ID obtained from the previous command.
Step 3: Change the Port Number
If terminating the process is not an option, or if the port is used by another essential service, consider changing the port number in your NestJS application configuration. You can do this by modifying the main.ts file or the environment configuration:
const port = process.env.PORT || 3001;
Ensure that the new port number is not in use.
Additional Resources
For more information on managing ports and processes, you can refer to the following resources:
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Javascript NestJS Error: EADDRINUSE, Address already in use
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