Linux环境下React Native npm start报错（端口8081被占用）及相关问题

Hey there, let's cut straight to the core of your issue: that Error: listen EADDRINUSE :::8081 line makes it clear the default Metro Bundler port (8081) is already occupied by another process. That's why your npm start fails, and react-native run-android gets stuck loading—your app can't connect to the bundler it needs to load code.

You've already tried some general React Native troubleshooting steps (cleaning node_modules, reinstalling watchman), but let's target the port conflict directly with these solutions:

1. Identify and Kill the Process Using Port 8081 #

First, find out which program is hogging the port:

• Run this command to list processes using port 8081:

  lsof -i :8081
  

  Look for the PID column (the numerical ID of the process using the port).
• If lsof isn't installed on your system, use this alternative command:

  netstat -tulpn | grep 8081
  

• Once you have the PID, terminate the process with:

  sudo kill -9 <PID>
  

  Replace <PID> with the actual number you found (e.g., sudo kill -9 1234).

2. Start Metro on a Different Port (If You Need to Keep 8081 in Use) #

If you can't kill the process using 8081, just tell Metro to use an alternative port:

• Start the bundler with a custom port:

  npm start -- --port 8082
  

• Then run your Android app pointing to the new port:

  react-native run-android --port 8082
  

• To make this permanent, add a metro.config.js file in your project root with:

  module.exports = {
    server: {
      port: 8082,
    },
  };
  

3. Extra Troubleshooting to Cover All Bases #

Since you already tried reinstalling node_modules and watchman, add these checks to ensure everything is working:

• Reset Metro's cache (this often fixes stuck loading issues even after resolving port conflicts):

  npx react-native start --reset-cache
  

• After reinstalling watchman, close your terminal and open a new one to ensure the changes take effect.
• Verify watchman is installed correctly with:

  watchman version
  

Quick Note on Your Project Setup #

Your package.json looks completely standard for React Native 0.59.5—no configuration issues stand out here. The problem is 100% related to the port conflict, not your project's dependencies or scripts.

Give these steps a try, and your app should load properly once Metro can start up successfully!

内容的提问来源于stack exchange，提问作者mad_greasemonkey