How to fix Error: Invalid HTTP version (unsupported protocol) in Node.js

# Test HTTP/1.1 (default)
curl -v http://example.com

# Test HTTP/2
curl --http2 -v https://example.com

# Test HTTP/3 (QUIC)
curl --http3 -v https://example.com

# Check response headers and protocol version
curl -i http://example.com | head -20

const http = require('http');
const https = require('https');

// Standard HTTP/1.1 request (default)
const req = https.get('https://example.com', (res) => {
  console.log(`Protocol: ${res.httpVersion}`); // Should be "1.1" or "2.0"
  res.pipe(process.stdout);
});

req.on('error', (err) => {
  console.error('Request error:', err.message);
});

const https = require('https');

const options = {
  hostname: 'example.com',
  port: 443,
  path: '/',
  method: 'GET',
  // Disable HTTP/2 for compatibility with some proxies
  http2: false,
};

const req = https.request(options, (res) => {
  console.log(`Status: ${res.statusCode}`);
  res.on('data', (chunk) => {
    process.stdout.write(chunk);
  });
});

req.on('error', (err) => {
  console.error('Request error:', err.message);
});

req.end();

upstream backend {
  server backend-server:3000;
  # Ensure proxy passes valid HTTP versions
}

server {
  listen 80;
  server_name example.com;

  location / {
    proxy_pass http://backend;
    # Explicitly set HTTP version
    proxy_http_version 1.1;
    proxy_set_header Connection "";
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  }
}

# Check current Node.js version
node --version

# Update Node.js using nvm (recommended)
nvm install --lts
nvm use --lts

# Or update via your package manager
# macOS
brew upgrade node

# Ubuntu/Debian
sudo apt update && sudo apt upgrade nodejs

# Verify update
node --version

const https = require('https');

async function fetchWithFallback(url, options = {}) {
  const httpVersions = ['1.1', '1.0']; // Fallback sequence

  for (const version of httpVersions) {
    try {
      console.log(`Attempting with HTTP/${version}...`);

      const opts = {
        ...options,
        http2: version !== '1.0' && version !== '1.1',
      };

      return await new Promise((resolve, reject) => {
        https.get(url, opts, (res) => {
          let data = '';
          res.on('data', (chunk) => data += chunk);
          res.on('end', () => resolve(data));
        }).on('error', reject);
      });
    } catch (err) {
      console.error(`Failed with HTTP/${version}: ${err.message}`);
      if (version === httpVersions[httpVersions.length - 1]) {
        throw err; // All versions failed
      }
    }
  }
}

fetchWithFallback('https://example.com')
  .then((data) => console.log('Success:', data))
  .catch((err) => console.error('All attempts failed:', err.message));

# Capture HTTP traffic with tcpdump
sudo tcpdump -i any -A 'tcp port 443 or tcp port 80' | grep -i 'HTTP'

# Or use Wireshark for GUI packet inspection
wireshark

# Use curl with maximum verbosity
curl -vvv http://example.com 2>&1 | head -40

# Check for Node.js HTTP debug logs
NODE_DEBUG=http node your-script.js 2>&1 | head -50