Javascript Express Error: listen EADDRINUSE
Understanding Express.js
Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. It facilitates the rapid development of Node-based web applications by providing a simple interface to create APIs and handle HTTP requests.
Identifying the Symptom: Error: listen EADDRINUSE
When working with Express.js, you might encounter the error message: Error: listen EADDRINUSE. This error typically appears when you attempt to start your Express server, and it indicates that the port you are trying to use is already occupied by another process.
Details About the Issue
What Does EADDRINUSE Mean?
The error code EADDRINUSE stands for 'Error Address In Use'. It occurs when a network port is already in use by another application or process. In the context of Express.js, this means that the port you specified in your app.listen() method is not available.
Common Causes
This issue often arises when:
- You have another instance of your application running.
- Another application is using the same port.
- The previous instance of the application did not shut down properly.
Steps to Fix the Issue
Step 1: Identify the Process Using the Port
To resolve this issue, you first need to identify which process is using the port. You can do this by running the following command in your terminal:
lsof -i :
Replace <PORT_NUMBER> with the port number you are trying to use. This command will list the process ID (PID) of the application using the port.
Step 2: Terminate the Process
Once you have the PID, you can terminate the process using the following command:
kill -9 <PID>
Replace <PID> with the actual process ID. Be cautious when using kill -9 as it forcefully stops the process.
Step 3: Use a Different Port
If terminating the process is not an option, consider using a different port for your Express application. You can change the port number in your app.listen() method:
app.listen(3001, () => {
console.log('Server is running on port 3001');
});
Additional Resources
For more information on managing ports and processes, you can refer to the following resources:
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