CoAP POST Request Not Creating Resource

In this tutorial, you'll learn about CoAP POST Request Not Creating Resource. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

The Problem

CoAP POST creates a resource but the server returns 4.00 Bad Request.

Quick Fix

Wrong

server.on('request', (req, res) => {
  // No path matching — all requests same handler
  res.code = '2.01'  # Created
  res.end(req.payload)
})

Client receives 2.01 Created but resource path is not returned.

Right

server.on('request', (req, res) => {
  if (req.method === 'POST' && req.url === '/devices') {
    const deviceId = 'device-' + Date.now()
    
    // Store resource
    devices[deviceId] = JSON.parse(req.payload.toString())
    
    // Return 2.01 Created with location
    res.code = '2.01'
    res.setOption('Location-Path', ['devices', deviceId])
    res.end(JSON.stringify({ id: deviceId }))
  } else if (req.method === 'POST') {
    res.code = '4.00'
    res.end('Bad Request: use /devices')
  }
})

Client receives 2.01 Created with Location-Path option pointing to new resource.

Prevention

CoAP POST creates a sub-resource (like HTTP POST). Return 2.01 Created with Location-Path option. Validate the request payload before creating. CoAP PUT replaces or creates at the specified path (idempotent).

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

FAQ