The Constrained Application Protocol (CoAP) (https://datatracker.ietf.org/doc/draft-ietf-core-coap/) is a RESTful web transfer protocol for resource-constrained networks and nodes. CoAP.NET is an implementation in C# providing CoAP-based services to .NET applications. Reviews and suggestions would be appreciated.

Copyright (c) 2011-2015, Longxiang He [email protected], SmeshLink Technology Co.

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• Acknowledgements

The C# implementation is available in the NuGet Package Gallery under the name Com.AugustCellars.CoAP. To install this library as a NuGet package, enter 'Install-Package Com.AugustCellars.CoAP' in the NuGet Package Manager Console.

Documentation can be found in two places. First an XML file is installed as part of the package for inline documentation. Additionally, I have started working on the Wiki associated with this project.

CoAP sessions are considered as request-response pair.

Access remote CoAP resources by issuing a Request and receive its Response(s).

  // new a GET request
  Request request = new Request(Method.GET);
  request.URI = new Uri("coap://[::1]/hello-world");
  request.Send();
  
  // wait for one response
  Response response = request.WaitForResponse();

There are 4 types of request: GET, POST, PUT, DELETE, defined as Method.GET, Method.POST, Method.PUT, Method.DELETE.

Responses can be received in two ways. By calling request.WaitForResponse() a response will be received synchronously, which means it will block until timeout or a response is arrived. If more responses are expected, call WaitForResponse() again.

To receive responses asynchronously, register a event handler to the event request.Respond before executing.

Parsing Link Format

Use LinkFormat.Parse(String) to parse a link-format response. The returned enumeration of WebLink contains all resources stated in the given link-format string.

  Request request = new Request(Method.GET);
  request.URI = new Uri("coap://[::1]/.well-known/core");
  request.Send();
  Response response = request.WaitForResponse();
  IEnumerable<WebLink> links = LinkFormat.Parse(response.PayloadString);

See CoAP Example Client for more.

A new CoAP server can be easily built with help of the class CoapServer

  static void Main(String[] args)
  {
    CoapServer server = new CoapServer();
    
    server.Add(new HelloWorldResource("hello"));
    
    server.Start();
    
    Console.ReadKey();
  }

See CoAP Example Server for more.

CoAP resources are classes that can be accessed by a URI via CoAP. In CoAP.NET, a resource is defined as a subclass of Resource. By overriding methods DoGet, DoPost, DoPut or DoDelete, one resource accepts GET, POST, PUT or DELETE requests.

The following code gives an example of HelloWorldResource, which can be visited by sending a GET request to "/hello-world", and respones a plain string in code "2.05 Content".

  class HelloWorldResource : Resource
  {
      public HelloWorldResource()
          : base("hello-world")
      {
          Attributes.Title = "GET a friendly greeting!";
      }

      protected override void DoGet(CoapExchange exchange)
      {
          exchange.Respond("Hello World from CoAP.NET!");
      }
  }
  
  class Server
  {
      static void Main(String[] args)
      {
          CoapServer server = new CoapServer();
          server.Add(new HelloWorldResource());
          server.Start();
      }
  }

See CoAP Example Server for more.

I am currently sync-ed up to Visual Studio 2017 and have started using language features of C# v7.0 that are supported both in Visual Studio and in the latest version of mono.

See LICENSE for more info.

This is a copy of the CoAP.NET project hosted at (https://http://coap.codeplex.com/). As this project does not seem to be maintained anymore, and I am doing active updates to it, I have made a local copy that things are going to move forward on.

Current projects are:

• [OSCoAP]{https://datatracker.ietf.org/doc/draft-ietf-core-object-security/} - Add an implemenation of message based security
• [EDHOC]{https://datatracker.ietf.org/doc/draft-selander-ace-cose-ecdhe/} - Ephemeral Diffie-Hellman over COSE - a key establishment protocol
• DTLS - Support DTLS for transport
• [TLS/TCP]{https://datatracker.ietf.org/doc/draft-ietf-core-coap-tcp-tls/} - Support TCP and TLS over TCP for transport
• [Resource Directory]{https://datatracker.ietf.org/doc/draft-ietf-core-resource-directory/} - Resource directory resources
• [PubSub]{https://datatracker.ietf.org/doc/draft-ietf-core-coap-pubsub/} - Publish-Subscribe Broker
• [AAA]{https://datatracker.ietf.org/doc/draft-ietf-ace-oauth-authz/} - Authentication and authoriztion protocol work

CoAP.NET is based on Californium, a CoAP framework in Java by Matthias Kovatsch, Dominique Im Obersteg, and Daniel Pauli, ETH Zurich. See http://people.inf.ethz.ch/mkovatsc/californium.php. Thanks to the authors and their great job.