mbed TLS is described as '(formerly known as PolarSSL) makes it trivially easy for developers to include cryptographic and SSL/TLS capabilities in their (embedded) products, facilitating this functionality with a minimal coding footprint' and is an app in the Development category. There are six alternatives to mbed TLS for a variety of platforms, including Windows, Linux, Mac, BSD and iPad. The best alternative is OpenSSL, which is both free and Open Source. Other great apps like mbed TLS are LibreSSL (Free, Open Source), GnuTLS (Free, Open Source), wolfSSL (Free, Open Source) and Network Security Services (Free, Open Source).
Network Security Services (NSS) comprises a set of libraries designed to support cross-platform development of security-enabled client and server applications with an option support for hardware SSL acceleration on the server side and hardware smart cards on the client side.
The SSL/TLS and Certificate tutorial for Windows enables you to fast track your understanding of the SSL/TLS protocol, Certificate Management, and secure communication. The download includes many C source code examples, including a secure WebSocket tutorial.