Client applications usually use SSL/TLS protocol to send sensitive data such as passwords, credit card numbers, personal data. SSL/TLS protocol allows clients to authenticate the server and encrypt the data. The authentication of the server allows the client to make sure that the data will be sent to the expected addressee (and not to a malicious one). Data encryption guarantees that even if the transmitted data is intercepted somewhere on its way to the server, the interceptor will not be able to use it.

This recipe demonstrates how to implement a synchronous TCP client application supporting SSL/TLS protocol using the Boost.Asio and OpenSSL libraries. The TCP client application demonstrated in the recipe named Implementing synchronous TCP client from Chapter 3, Implementing Client Applications, is taken as a base for this recipe, and some code changes and additions are made to it in order to add support for SSL/TLS protocol. The code that differs...