Error: listen EADDRINUSE: address already in use

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# macOS/Linux: ポートを使用しているプロセスを確認
lsof -i :3000

# プロセスを終了
kill -9 <PID>

# Windows: ポートを使用しているプロセスを確認
netstat -ano | findstr :3000

# プロセスを終了
taskkill /PID <PID> /F

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// 環境変数でポートを指定
const PORT = process.env.PORT || 3001;

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

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import { createServer } from 'net';

function getAvailablePort(startPort) {
  return new Promise((resolve, reject) => {
    const server = createServer();
    server.listen(startPort, () => {
      const port = server.address().port;
      server.close(() => resolve(port));
    });
    server.on('error', () => {
      resolve(getAvailablePort(startPort + 1));
    });
  });
}

// 使用例
const port = await getAvailablePort(3000);
app.listen(port);

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

server.on('error', (error) => {
  if (error.code === 'EADDRINUSE') {
    console.error(`Port ${PORT} is already in use`);
    // 別のポートで再試行
    server.listen(PORT + 1);
  } else {
    throw error;
  }
});

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const server = app.listen(PORT);

// Graceful shutdown
process.on('SIGTERM', () => {
  server.close(() => {
    console.log('Server closed');
    process.exit(0);
  });
});

process.on('SIGINT', () => {
  server.close(() => {
    console.log('Server closed');
    process.exit(0);
  });
});

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{
  "scripts": {
    "dev": "node server.js",
    "dev:clean": "kill-port 3000 && node server.js"
  },
  "devDependencies": {
    "kill-port": "^2.0.1"
  }
}

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# docker-compose.yml
services:
  app:
    ports:
      - "${PORT:-3000}:3000"  # 環境変数でポートを指定可能に