lime-coap

About

lime-coap is a Constrained Application Protocol (CoAP) protocol server for the limerun project, based on OWIN-JS standard.

It servers CoAP messages in standard OWIN-JS format and allows existing middleware for Connect, Express and limerun projects to consume/send each mesage.

It is an open-source, standards-based, drop-in replacement for CoAP servers such as node-coap.

It uses the widely used library 'coap-packet' for protocol formatting.

Written in plain javascript for maximum portability to constrained devices

Makes CoAP messages look to an application just like an HTTP message so little or no application changes required to support multiple REST protocols

Status

Fully working prototype include server and client, multicast, etc.

Includes:

Server Functions

• Layered protocol based on native UDP sockets
• Translation from UDP Raw Message to CoAP Packet in standard OWIN-JS format, compatible with all HTTP and COAP applications including those written for Express, Connect, etc!
• Optional logging middleware for each inbound message
• Server and Client Request caching middleware
• Confirmable send middleware that keeps retrying until acknowledgements received
• Auto-Acknowledge middleware that automatically takes care of sending acknowledgements to inbound confirmable requests/responses
• Observable messages (publish/subscribe)

Client Functions

• Layered protocol based on native UDP sockets
• Translation from CoAP Packet in standard OWIN-JS format to CoAP Raw Message
• Optional logging middleware
• Client Request caching middleware
• Confirmable send middleware that keeps retrying until acknowledgements received
• Auto-Acknowledge middleware that automatically takes care of sending acknowledgements to inbound confirmable responses
• Observable messages (publish/subscribe)

Installation

npm install lime-coap

Usage

Simple Hello World Server and Client

const lime = require('limerun')
    , CoAP = require('lime-coap')      

var app = new lime.app();

app.use(function(next){
  this["owin.ResponseBody"].end('Hello World from ' + this["owin.RequestPath"]);
   return next();
    });

var server = CoAP.createServer(serverOptions, app.build());

server.listen(CoAP.constants.coapPort).then(function(){
   var context = server.clientCreateRequest('coap://224.0.1.187/device', "GET");
   context["owin.ResponseBody"].pipe(process.stdout);
   context["owin.ResponseBody"].on("response", function() {
   context["owin.ResponseBody"].on('end', function() {
       process.exit(0)
    });
  });
  
  context["owin.RequestBody"].end();

 });

Multicast and UniCast Server Client Example

const lime = require('limerun')
    , CoAP = require('./lib/index.js')      
    , Promise = require('bluebird')

var app = new lime.app();
app.use(function(next){
  this["owin.ResponseBody"].end('Hello World from ' + this["owin.RequestPath"]);
   return next();
    });
    
var serverOptions = {
    "server.LocalPortMulticast" : CoAP.constants.coapMulticastIPV4
  , "server.LocalPortReuse" : true
  , "server.IsGlobalClient" : false
}

var clientOptions = { "server.IsGlobalClient" : true
                    , "server.LocalPortReuse" : false}
                    
var client = CoAP.createServer(clientOptions);
var server = CoAP.createServer(serverOptions, app.build());

Promise.join(client.listen(0), server.listen(CoAP.constants.coapPort))
.then(function(){
   var context = server.clientCreateRequest('coap://224.0.1.187/projector', "GET");
   context["owin.ResponseBody"].pipe(process.stdout);
   context["owin.ResponseBody"].on("response", function() {
   context["owin.ResponseBody"].on('end', function() {
       process.exit(0)
    });
  });
  
  context["owin.RequestBody"].end();
})

Roadmap

Next steps are to build a reference framework to link together server, client, discovery and other protocol functions.

Adding additional features of the protocol such as Type 2 Blocks, is as simple as adding a new middleware function (10-30 lines of javascript)