SMCP — A Full-Featured Embedded CoAP Stack

SMCP is a highly-configurable CoAP stack which is suitable for a wide range of embedded devices, from bare-metal sensor nodes with kilobytes of RAM to Linux-based devices with megabytes of RAM.

Features include:

• Supports RFC7252
• Fully asynchronous I/O
• Supports both BSD sockets and µIP
• Sending and receiving asynchronous CoAP responses
• Observing resources and offering observable resources
• Retransmission of confirmable transactions
• Multicast groups (Working toward full RFC7390 support)
• Resource pairing
• [Experimental support for DTLS][https://github.com/darconeous/smcp/issues/35]

The package also includes smcpctl, a powerful command line tool for browsing and configuring CoAP nodes.

SMCP is currently working toward a v1.0 API. Until v1.0 is released, all APIs are subject to change.

Getting Help

If you are having trouble with SMCP, you can join the official SMCP mailing list and ask your questions there.

• SMCP Developers Group smcp-dev@googlegroups.com

Getting, building, and installing via Git

First:

$ git clone git://github.com/darconeous/smcp.git
$ cd smcp

To just build the latest tagged stable release:

$ git checkout latest-release
$ ./configure
$ make
$ sudo make install

For bleeding-edge:

$ git checkout master
$ git archive origin/autoconf/master | tar xv
$ ./configure
$ make
$ sudo make install

Getting, building, and installing from an archive

$ curl https://github.com/darconeous/smcp/archive/full/latest-release.zip > latest-release.zip
$ unzip latest-release.zip
$ cd smcp-latest-release
$ ./configure
$ make
$ sudo make install	

Installing via Homebrew on OS X

To get the "latest-release":

$ brew tap darconeous/embedded
$ brew install smcp

To get the bleeding-edge release:

$ brew tap darconeous/embedded
$ brew install smcp --HEAD

Node: This is mostly for people who just want to use smcpctl (described below). If you want to compile against SMCP, you'll currently need to grab the sources and build against them directly.

Getting Started

The best way to get started is to have a look at some example code which uses SMCP. There are several included examples:

• examples/example-1.c - Shows how to respond to a request.
• examples/example-2.c - Shows how to respond to a request for a specific resource.
• examples/example-3.c - Shows how to use the node router.
• examples/example-4.c - Shows how to make resources observable.

Additionally, there is the plugtest server and client, which can be found in src/plugtest.

The Contiki version of the plugtest uses the last two files. You can find the Contiki version at contiki-src/examples/smcp-plugtest/.

Configurability

One of the goals of SMCP is to implent a full-featured CoAP library, but most embedded applications don't need all of these capabilities. Because of this, SMCP is designed so that you can individually enable or disable features depending on your needs (See src/smcp/smcp-config.h).

For example, SMCP has the ability to have more than once instance, but embedded platforms will never need more than one. Passing around a reference to a global variable that will never change is wasteful, so when compiled with SMCP_EMBEDDED turned on, we transparently (via some preprocessor magic) ignore the reference to the SMCP instance from all of the functions that take it. This makes it easy to use the same codebase for both embedded and non-embedded applications. There are other configuration options for doing things like limiting malloc() usage, avoiding use of printf() (and variants), enabling/disabling observing, etc.

Contiki Support

SMCP fully supports Contiki. To build the Contiki examples, just make sure that the CONTIKI environment variable is set point to your Contiki root, like so:

$ cd contiki-src/examples/smcp-simple
$ make CONTIKI=~/Projects/contiki TARGET=minimal-net

API Documentation

You can find an online version of the API documentation here: http://darconeous.github.com/smcp/doc/html/

smcpctl

smcpctl is a command-line interface for browsing, observing, and interacting with CoAP devices. It is, for the most part, self-documenting: just type in smcpctl help. You can run individual commands directly from the command line when invoking smcpctl or you can invoke with no arguments and you will enter the smcpctl shell (CLI). The shell environment allows you to use familiar unix commands like ls, cd, and cat. The CLI supports quoting and tab-completion of resource names, which is incredibly handy.

Here are a few examples of how you can use it:

GET a resource

$ smcpctl get coap://coap.me/large

Listing the contents of a resource

$ smcpctl ls coap://coap.me/.well-known/core

PUT a resource and show parsed response headers

$ smcpctl put -i coap://coap.me/test "Testing out smcpctl's PUT command"

Observe a resource for changes

$ smcpctl observe coap://vs0.inf.ethz.ch/obs

smcpd

smcpd is a CoAP daemon that is eventually intended to be a flexible CoAP server for Linux and other unix-like machines. It is a work in progress.

Plugtests

smcp-plugtest-server implements some of the ESTI plugtests for CoAP.

List of Public Test Servers

• coap://coap.me/
• coap://vs0.inf.ethz.ch/

Authors and Contributors

• Robert Quattlebaum darco@deepdarc.com