How to fix Error: connect ECONNREFUSED 127.0.0.1:5000 (port not listening) in Node.js

# Check if any process is listening on the port
lsof -i :5000
# or on Linux
netstat -tuln | grep :5000
# or use ss command
ss -tuln | grep :5000

# For a Node.js application
node server.js
# For a development server
npm run dev
# For a database like PostgreSQL
sudo systemctl start postgresql

// Check your connection configuration
const PORT = process.env.PORT || 5000; // Make sure this matches

// For HTTP requests
const response = await fetch(`http://localhost:${PORT}/api`);

// For database connections
const client = new Client({
  host: 'localhost',
  port: 5432, // Ensure this matches your database server
  database: 'mydb'
});

// Server binding to all interfaces (accessible from anywhere)
app.listen(PORT, '0.0.0.0', () => {
  console.log(`Server running on all interfaces port ${PORT}`);
});

// Server binding only to localhost (only local connections)
app.listen(PORT, '127.0.0.1', () => {
  console.log(`Server running on localhost:${PORT}`);
});

// In containerized environments
const HOST = '0.0.0.0';
const PORT = 5000;
app.listen(PORT, HOST);

async function connectWithRetry(url, maxRetries = 5, delay = 1000) {
  for (let i = 0; i < maxRetries; i++) {
    try {
      const response = await fetch(url);
      console.log('Connected successfully');
      return response;
    } catch (err) {
      if (err.code === 'ECONNREFUSED') {
        console.log(`Connection refused, retry ${i + 1}/${maxRetries}`);
        if (i < maxRetries - 1) {
          await new Promise(resolve => setTimeout(resolve, delay));
          delay *= 2; // Exponential backoff
        } else {
          throw new Error('Max retries reached, server not available');
        }
      } else {
        throw err; // Different error, don't retry
      }
    }
  }
}

// Usage
try {
  await connectWithRetry('http://localhost:5000/health');
} catch (err) {
  console.error('Failed to connect:', err.message);
}

# Temporarily test with firewall disabled (Linux)
sudo ufw status
sudo ufw allow 5000/tcp

# Windows - check Windows Defender Firewall
# Add inbound rule for your port in Windows Defender settings

# macOS - check if Little Snitch or similar software is blocking

// Bypass proxy for localhost in Node.js
process.env.NO_PROXY = 'localhost,127.0.0.1';

const http = require('http');

const options = {
  hostname: 'localhost',
  port: 5000,
  path: '/api',
  method: 'GET'
};

const req = http.request(options, (res) => {
  console.log(`Status: ${res.statusCode}`);
  res.on('data', (data) => console.log(data.toString()));
});

req.on('error', (err) => {
  if (err.code === 'ECONNREFUSED') {
    console.error('Cannot connect to server on port 5000');
    console.error('Please ensure the server is running');
    console.error('Start it with: npm run server');
  } else {
    console.error('Connection error:', err);
  }
});

req.end();