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david
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CoAP server with Rack interface.
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david
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# David [](http://badge.fury.io/rb/david) [](https://travis-ci.org/nning/david) [](https://coveralls.io/r/nning/david) [](https://codeclimate.com/github/nning/david) [](https://hub.docker.com/r/nning2/david/) David is a CoAP server with Rack interface to bring the illustrious family of Rack compatible web frameworks into the Internet of Things. It is tested with MRI >= 2.3, and JRuby >= 9.1. David version ~> 0.5.0 aims for Rack 2 (and Rails 5). Compatibility to Rails 4 is available in version ~> 0.4.5. ## Quick Start Just include David in your Gemfile! gem 'david' It will hook into Rack and make itself the default handler, so running `rails s` starts David. If you want to start WEBrick for example, you can do so by executing `rails s webrick`. **For now, you have to remove the `web-console` gem from the Gemfile (which is HTTP specific anyway) if you use Rails/David in CoAP only mode.** You probably also want to disable [CSRF protection](http://api.rubyonrails.org/classes/ActionController/RequestForgeryProtection/ClassMethods.html) by removing the `protect_from_forgery` line from `app/controllers/application_controller.rb` (or use `:null_session` if you know what you are doing). The [`coap-rails-dummy`](https://github.com/nning/coap-rails-dummy) repository documents [changes to a newly generated Ruby on Rails application for a quick start](https://github.com/nning/coap-rails-dummy/compare/initial...master). After the server is started, the Rails application is available at `coap://[::1]:3000/` by default. (Although you have to set a route for `/` in `config/routes.rb`, of course.) [Copper](https://addons.mozilla.org/de/firefox/addon/copper-270430/) is a CoAP client for Firefox and can be used for development. The [Ruby coap gem](https://github.com/nning/coap) is used by David for example for message parsing and also includes a command line utility (named `coap`) that can also be used for development. As [CoAP](https://tools.ietf.org/html/rfc7252) is a protocol for constrained environments and machine to machine communications, returning HTML from your controllers will not be of much use. JSON for example is more suitable in that context. The Accept header is set to "application/json" by default, so that Rails responds with the JSON resource representation. David works well with the default ways to handle JSON responses from controllers such as `render json:`. You can also utilize [Jbuilder templates](https://github.com/rails/jbuilder) for easy generation of more complex JSON structures. [CBOR](https://tools.ietf.org/html/rfc7049) can be used to compress your JSON. Automatic transcoding between JSON and CBOR is activated by setting the Rack environment option `CBOR` or `config.coap.cbor` in your Rails application config to `true`. ## Tested Rack Frameworks By providing a Rack interface, David does not only work with Rails but also with the following Rack compatible web frameworks. * [Grape](https://github.com/intridea/grape) * [Hobbit](https://github.com/patriciomacadden/hobbit) * [NYNY](https://github.com/alisnic/nyny) * Plain Rack * [Sinatra](https://github.com/sinatra/sinatra) * [Rails](https://github.com/rails/rails) * [Roda](https://github.com/jeremyevans/roda) ## Configuration The following table lists available configuration options for the CoAP server. Rack keys can be specified with the `-O` option of `rackup`. The listed Rails keys can be accessed for example from the `config/application.rb` file of your Rails application. | Rack key | Rails key | Default | Semantics | |--- |--- |--- |--- | | Block | coap.block | true | [Blockwise transfers](https://tools.ietf.org/html/draft-ietf-core-block-16) | | CBOR | coap.cbor | false | JSON/CBOR transcoding | | DefaultFormat | coap.default_format | | Default Content-Type | | Host | | ::1 / :: | Server listening host | | Log | | info | Log level (none or debug) | | MinimalMapping | | false | Minimal HTTP status codes mapping | | Multicast | coap.multicast | true | Multicast support | | MulticastGroups | coap.multicast_groups | ff02::fd, ff05::fd | Multicast group configuration | | Observe | coap.observe | true | [Observe support](https://tools.ietf.org/html/draft-ietf-core-observe-16) | | | coap.only | true | Removes (HTTP) middleware | | Port | | 5683 | Server listening port | | | coap.resource_discovery | true | Provision of `.well-known/core` | The server can be started with debug log level for example with the following command provided that a rackup config file (`config.ru`) exists like in a Rails application. rackup -O Log=debug In a Rails application, CBOR transcoding is activated for any controller and action by inserting the third line of the following code into `config/application.rb`. module Example class Application < Rails::Application config.coap.cbor = true end end In Copper for example the default block size for Blockwise Transfers is set to 64 bytes. That's even small for most exception messages. It is recommended to set the block size to the maximum (1024B) during development. ## Discovery The [CoAP Discovery](https://tools.ietf.org/html/rfc7252#section-7) will be activated by default. A `.well-known/core` resource automatically returns the resources you defined in Rails. You can annotate this resources with attributes like an interface description (`if`) or the content type (`ct`). (See [RFC6690](https://tools.ietf.org/html/rfc6690) or [the code](https://github.com/nning/coap/blob/master/lib/core/link.rb#L8) for further documentation.) class ThingsController < ApplicationController discoverable \ default: { if: 'urn:things', ct: 'application/cbor' }, index: { if: 'urn:index' } def show render json: Thing.find(params[:id]) end def index render json: Thing.all end end ## Rack environment David sets the following server (and protocol) specific Rack environment entries that can be read from your Rack application if necessary. | Key | Value class | Semantics | |--- |--- |--- | | coap.version | Integer | Protocol version of CoAP request | | coap.multicast | Boolean | Marks whether request was received via multicast | | coap.dtls | String | DTLS mode (as defined in [section 9 of RFC7252](https://tools.ietf.org/html/rfc7252#section-9)) | | coap.dtls.id | String | DTLS identity | | coap.cbor | Object | Ruby object deserialized from CBOR | ## Benchmarks David handles about 12,500 requests per second in MRI and 14,000 in JRuby (tested in MRI 2.3.0 and JRuby 1.7.19 with up to 10,000 concurrent clients on a single core of a Core i7-3520M CPU running Linux 3.18.6). ## Caveats * Incoming block-wise transfer is not supported. * Automatically generating `.well-known/core` is only supported in Rails. ## Copyright The code is published under the MIT license (see the LICENSE file). ### Authors * [henning mueller](https://nning.io)
