Fix: "Error: listen EADDRINUSE" in Node.js (Port Already in Use)

# Find process using port 3000
lsof -i :3000

# Kill process by PID
kill -9 <PID>

# Or kill directly
lsof -ti:3000 | xargs kill -9

# Find all Node.js processes
ps aux | grep node

# Kill all Node.js processes (use carefully)
pkill -f node

# Find process using port 3000
netstat -ano | findstr :3000

# Kill process by PID
taskkill /PID <PID> /F

# Find all Node.js processes
tasklist | findstr node

# Kill all Node.js processes
taskkill /F /IM node.exe

const express = require('express');
const app = express();

// Use environment variable or default to 3000
const PORT = process.env.PORT || 3000;

app.get('/', (req, res) => {
  res.json({ message: 'Server running' });
});

app.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
});

// Start with different port:
// PORT=3001 node server.js

// .env file
PORT=3001

// server.js
require('dotenv').config();
const express = require('express');
const app = express();

const PORT = process.env.PORT || 3000;

app.listen(PORT, () => {
  console.log(`Server on port ${PORT}`);
});

const express = require('express');
const app = express();

function startServer(port) {
  app.listen(port, () => {
    console.log(`Server running on port ${port}`);
  }).on('error', (err) => {
    if (err.code === 'EADDRINUSE') {
      console.log(`Port ${port} is in use, trying ${port + 1}`);
      startServer(port + 1);
    } else {
      console.error('Server error:', err);
    }
  });
}

const PORT = process.env.PORT || 3000;
startServer(PORT);

# Install PM2
npm install -g pm2

# Start server with PM2
pm2 start server.js

# Stop server
pm2 stop server.js

# List all processes
pm2 list

# Kill all processes
pm2 kill

# PM2 handles process cleanup automatically