Coap Security

In this tutorial, you'll learn about CoAP DTLS Handshake Fails. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

The Problem

CoAP over DTLS (coaps://) connection fails during handshake.

Quick Fix

Wrong

coap.request('coaps://localhost/temp')  # No certificate

DTLS handshake fails — certificate error or timeout.

Right

const coap = require('coap')
const fs = require('fs')

// Server with DTLS
const options = {
  key: fs.readFileSync('./server-key.pem'),
  cert: fs.readFileSync('./server-cert.pem'),
  ca: fs.readFileSync('./ca-cert.pem'),
  requestCert: true,  // Mutual TLS
  rejectUnauthorized: true
}

const server = coap.createServer({ type: 'udp6', dtls: options })

server.listen(5684, () => {
  console.log('CoAPS server on port 5684')
})

// Client with DTLS
const req = coap.request({
  hostname: 'localhost',
  port: 5684,
  pathname: '/temp',
  agent: new coap.Agent({
    type: 'udp6',
    dtls: {
      key: fs.readFileSync('./client-key.pem'),
      cert: fs.readFileSync('./client-cert.pem'),
      ca: fs.readFileSync('./ca-cert.pem')
    }
  })
})

DTLS handshake successful, secure CoAP communication established.

Prevention

DTLS = Datagram TLS (UDP version of TLS). Port 5684 (coaps://). Self-signed certs need to be trusted or disable verification. DTLS 1.2 is most common. DTLS handshake overhead adds latency (3 round trips). For constrained devices, use raw public key (RPK) instead of X.509 certificates.

DodaTech engineers apply these same patterns across Doda Browser, DodaZIP, and Durga Antivirus Pro for production IoT reliability.

FAQ