How do I write an async method with Tokio?

Question

I'm trying to write a library that will connect to remote servers and exchange data. I did this in C++ using Boost::Asio and am trying to do the same with Rust.

One of the problems I have is mapping concepts from Asio, like async_write/read to Tokio, starting with the fact that seemingly all Tokio examples demand that I replace my main() with an async main() , while I would like to encapsulate all my async code in structures and associated implementations.

Is it possible to use Tokio without replacing main() ? Is mio perhaps the only way?

Answer 1

You can create a runtime manually using Runtime::new() which is what the tokio main macro is doing under the hood. It's just for an awful lot of apps, especially examples that's just boilerplate. So the macro automates the simple case.

However, depending on the context of your library, it may be more idiomatic to provide a future based API, and then leave the app consumer to set up the runtime.