CoAP Observer Try

coap-server.js

#!/usr/bin/env node

/*
HOW TO:
1) install required tools
  - npm install coap --save
  - npm install coap-cli -g
2) run the server: chmod +x coap-server.js && ./coap-server.js
3) observe a resource 
  - coap get -o coap://localhost/message
4) publish a message
  - echo -n 'hello world asdf' | coap put coap://localhost/message
*/

/*
TO-DO
 - proper client session handling: clean up closed observer connections etc.
*/

const coap        = require('coap'),
  server      = coap.createServer(), 
  requests    = [];


function storeRequestConnection(req, res) {
  requests.push({url: req.url, connection: res, writeClb: res.write, end: res.end});
}

function isObserveRequest(req) {
  return req.headers.Observe === 0;
}

server.on('request', function(req, res) {

  if (isObserveRequest(req)) {
    storeRequestConnection(req, res);
  }

  if (req.headers.Observe !== 0)  {
    console.log('no observe');
    res.end('');
  }

  requests.filter(function(item) {
    return item.url === req.url;
  }).map(function (response) {
    response.writeClb.call(response.connection, 'llt ' + req.payload.toString() + 'length ' + requests.length);
  });

  if (req.payload.toString() === 'quit') {
    requests.map(function (response) {
      response.end.call(response.connection, 'quit');
    });
    res.end('');
    process.exit(0);
  }
});



// the default CoAP port is 5683
server.listen(function () {});