Asynchronous programming is commonly employed for efficient implementation of network interactions in C++. The essence of this approach lies in the fact that the results of socket read/write functions are not immediately available but become accessible after some time. This approach allows for loading the processor with useful work during the wait for data. Various implementations of this approach exist, such as callbacks, actors, future/promise, coroutines. In C++, these implementations are available as libraries from third-party developers or can be implemented independently.
Coroutines are the most challenging to implement as they require writing platform-dependent code. However, the recent version of the C++ 20 language standard introduces support for coroutines at the compiler and standard library levels. Coroutines are functions that can suspend their execution, preserving their state, and later return to that state to resume the function's work. The compiler automatically creates a checkpoint with the coroutine's state.
For a comprehensive understanding of C++ 20 coroutines, refer to this article. Below, we examine a code example using coroutines and describe important points applied during implementation.