Coap Server

This CoAP server is designed to be highly configurable to allow its use with a variety of IoT devices, for testing or for low-scale use.

Docker images:

Current Features:

• CoAP via UDP, DTLS, TCP, and TLS
  • Currently only PEM keys/certificates are supported
• GET, PUT, and POST
  • GET: Returns the value of the resource
  • PUT,POST: Print the sent data, and/or set the current value of the resource
• Resource observation
• Multiple data format support
  • STRING - Plaintext
  • HEX - Raw data represented as hex
  • BASE64 - Raw data represented as base64
• Logging to a separate file for each resource
• Execute external command on request data
  • By piping request data via stdin, or passing in via environment variable
• Templated resource configuration for creating multiple similar resources
• Regex-based on-the-fly resource creation
• Backing resource data by data files
  • Including notifying observers when file changes
• Multi-block requests
  • Currently no support for multi-block responses

Planned Features:

• See GitHub issues: https://github.com/farlepet/coapserver/issues

Running via Docker

coapserver images are build to support amd64, arm64, armv6, armv6, and i386 targets. coapserver-extra is currently only built to support amd64, due to -Wnarrowing errors thrown by the msgpack-tooks build on other platforms.

NOTE: Depending on the host system (for instance, podman on CentOS), it may be required to append a ,Z to the end of both bind mounts to work with SELinux.

docker run -it --rm -p 5683:5683/udp \
           --mount type=bind,source=$PWD/config.json,target=/config.json \
           --mount type=bind,source=$PWD/logs/,target=/var/log/coapserver \
           farlepet/coapserver:<version> \
           -c /config.json -l /var/log/coapserver

OR

docker run -it --rm -p 5683:5683/udp \
           --mount type=bind,source=$PWD/config.json,target=/config.json \
           --mount type=bind,source=$PWD/logs/,target=/var/log/coapserver \
           farlepet/coapserver-extra:<version> \
           -c /config.json -l /var/log/coapserver

Building

Requirements:

• g++/clang++
• make
• cmake
• libcoap 3: https://github.com/obgm/libcoap
• nlohmann JSON: https://github.com/nlohmann/json
  • Extra header (nlohmann/json_fwd.hpp) required - used to speed up compilation
• boost >= 1.65.0: https://www.boost.org/

Available library packages:

• Debian: nlohmann-json3-dev, libcoap3-dev, libboost-all-dev
• Arch Linux: libcoap (AUR), nlohmann-json, boost, msgpack-cxx

Building:

mkdir build && cd build
cmake ../ [options]
make

The following CMake options may be useful:

• -DCMAKE_CXX_COMPILER=<...>
  • Choose which c++ compiler to use
  • Tested with g++ and clang++

Manually building Docker image(s)

NOTE: Dockerfiles now expect to be run using docker buildx build, and will not work with standard docker build (unless having previously run docker buildx install).

# Build base coapserver image
docker buildx build -t coapserver .
# Build extra coapserver image - optional (base image must be built first)
# Adds extra tools including cbor2json, msgpack2json, lz4, gzip, and xz
docker buildx build -f Dockerfile.extra -t coapserver-extra .

Running Test Cases

Test cases are written in BATS and expect, both of these must be installed prior to running a test case.

To run the entire test suite:

bats tests/

To run a specific set of tests:

bats tests/<test>.bat

This must be run from the root of the repository, and the coap_server binary must be present at build/coap_server, as with the build process mentioned above.

Data Flow

PUT/POST:

• Request -> Formatter -> Command -> Log

GET:

• Current Resource Value -> Requestor