This is a simple lib to interact with TCP sockets in Linux/POSIX systems. It also has an extense openSSL-based API to handle security (hash, HMAC, cypher, EC asymmetric keys, etc).
In the apps folder there is an example how to use it. The example is an heartbeat application, first you need to setup the keys with keyManager, then use heartbeat app to send/receive heartbeats.
File src/sslUtility.c has the security features implementation using openSSL C API (make sure you have openSSL library installed before compiling). File src/tcpSocketLib.c implements the TCP sockets/connections API. Include the header include/tcpSocketLib.h in your project to use this library.
This library was tested in Ubuntu 18.04, besides openssl it requires the dependencies in deps to be compiled, they handle threading and command line input.