Transport Protocols

The DNS client supports multiple transport protocols, each with its own benefits and use cases.

Available Protocols

UDP (Default)

• Traditional DNS protocol
• Port 53
• Best for small queries
• Automatic fallback to TCP for truncated responses

// UDP (default)
const client = new DnsClient({
  domains: ['example.com'],
  type: 'A',
  udp: true // optional, this is default
})

TCP

• Reliable for larger responses
• Port 53
• Required for responses > 512 bytes
• Better for bulk queries

const client = new DnsClient({
  domains: ['example.com'],
  type: 'A',
  tcp: true
})

DNS-over-TLS (DoT)

• Encrypted DNS queries
• Port 853
• Prevents eavesdropping
• Certificate validation

const client = new DnsClient({
  domains: ['example.com'],
  type: 'A',
  tls: true,
  nameserver: 'dns.cloudflare.com' // DoT provider
})

DNS-over-HTTPS (DoH)

• HTTPS-encrypted DNS
• Port 443
• Firewall-friendly
• HTTP/2 benefits

const client = new DnsClient({
  domains: ['example.com'],
  type: 'A',
  https: true,
  nameserver: 'https://cloudflare-dns.com/dns-query'
})

Transport Configuration

You can configure transport-specific options:

const client = new DnsClient({
  domains: ['example.com'],
  transport: {
    type: 'tcp',
    timeout: 5000, // 5 seconds
    retries: 3 // Retry 3 times
  }
})

CLI Usage

# UDP (default)
dnsx example.com

# TCP
dnsx example.com -T

# DNS-over-TLS
dnsx example.com -S

# DNS-over-HTTPS
dnsx example.com -H --nameserver https://cloudflare-dns.com/dns-query

Best Practices

1. Default Choice: Use UDP for standard queries
2. Large Responses: Use TCP for zones with many records
3. Privacy: Use DoT or DoH when privacy is important
4. Firewalls: Use DoH if standard DNS ports are blocked
5. Reliability: Configure timeouts and retries for unreliable networks

Error Handling

Each transport implements proper error handling:

• Connection timeouts
• Network errors
• Protocol-specific errors (e.g., TLS certificate validation)
• Automatic retry with exponential backoff

Advanced Usage

For more advanced transport configurations and examples, see the Advanced Transport section.