These directories provide a user data (sockets) interface. The API presented is a Berkeley sockets API, similar to that of LWIP, allowing the files here to replace LWIP.
The directories include only the API and pure C source files that make no reference to a platform or an operating system. They rely upon the port directory to map to a target platform and provide the necessary build/test infrastructure for that target platform; see the relevant platform directory under port for build and usage information.
A usage example can be found in the README.md file for the common/network API.
The test directory contains generic tests for this API. Please refer to the relevant platform directory of the port component for instructions on how to build and run the tests. The tests use the common/network API and its test configuration data to provide a transport for the sockets testing.