Troubleshooting Guide: How to Resolve 'Metro Bundler Can't Listen on Port 8081' Error

If you are developing a React Native project, you might have encountered the error message "Metro Bundler can't listen on port 8081" while trying to run your app. This error can be frustrating and can halt your development process. In this guide, we will provide you with a step-by-step solution on how to resolve this error.

What Causes the 'Metro Bundler Can't Listen on Port 8081' Error?

The 'Metro Bundler Can't Listen on Port 8081' error can be caused due to several reasons, including:

• Port 8081 is already in use by another process.
• The Metro Bundler process has stopped running or has crashed.
• The React Native project is unable to access the required files.

Step-by-Step Solution to Resolve the 'Metro Bundler Can't Listen on Port 8081' Error

Follow these steps to resolve the 'Metro Bundler Can't Listen on Port 8081' error:

Step 1: Check if Port 8081 is Already in Use

The first step is to check if port 8081 is already in use by another process. To do this, follow these steps:

1. Open the command prompt or terminal on your computer.
2. Type the following command and press Enter: netstat -aon | findstr :8081
3. If you see any output, it means that port 8081 is already in use. Note down the Process ID (PID) of the process using the port.

Step 2: Kill the Process Using Port 8081

Once you have identified the process using port 8081, you need to kill the process. To do this, follow these steps:

1. Open the command prompt or terminal on your computer.
2. Type the following command and press Enter: taskkill /PID <PID> /F
   (Replace <PID> with the Process ID you noted down in Step 1)
3. Once the process is killed, try running your React Native project again.

Step 3: Restart the Metro Bundler Process

If the above steps did not resolve the error, you need to restart the Metro Bundler process. To do this, follow these steps:

1. Open the command prompt or terminal on your computer.
2. Navigate to your React Native project directory.
3. Type the following command and press Enter: npm start --reset-cache
4. Wait for the Metro Bundler process to start and try running your React Native project again.

Step 4: Check if the Required Files are Accessible

If the above steps did not resolve the error, you need to check if the required files are accessible. To do this, follow these steps:

1. Open the command prompt or terminal on your computer.
2. Navigate to your React Native project directory.
3. Type the following command and press Enter: adb reverse tcp:8081 tcp:8081
4. Wait for the command to execute and try running your React Native project again.

FAQ

Q1. What is Metro Bundler?

Metro Bundler is a JavaScript bundler for React Native that creates a bundle of your JavaScript code, assets, and other dependencies.

Q2. How do I know which process is using port 8081?

You can use the netstat -aon | findstr :8081 command to identify the process using port 8081. Note down the Process ID (PID) of the process to kill it.

Q3. What does the npm start --reset-cache command do?

The npm start --reset-cache command starts the Metro Bundler process and resets the cache.

Q4. What does the adb reverse tcp:8081 tcp:8081 command do?

The adb reverse tcp:8081 tcp:8081 command forwards the device's port 8081 to your computer's port 8081.

Q5. Can I change the default port used by Metro Bundler?

Yes, you can change the default port used by Metro Bundler by adding the --port flag followed by the desired port number. For example, npm start --port=8082.

Related Links

• React Native Troubleshooting Guide
• Metro Bundler Documentation
• ADB Documentation