multithread boost-asio server (vs boost async server tutorial)

Question

I'm following the boost-asio tutorial and don't know how to make a multi-threaded server using boost. I've compiled and tested the daytime client and daytime synchronous server and improved the communication (server asks the client for a command, processes it and then returns the result to the client). But this server can handle only one client at one time.

I would like to use boost to make a multi-threaded server. There is also daytime asynchronous server which executes

boost::asio::io_service io_service;
tcp_server server(io_service);
io_service.run();

in the main program function. The question is - is boost creating a thread for each client somewhere inside? Is this a multi-threaded solution? If not - how to make a multi-threaded server with boost? Thanks for any advice.

Answer 1

have a look at this tutorial. in short terms:

• io_service.run() in multiple threads gives a thread pool
• multiple io_services give completely separated threads

Answer 2

You don't need to explicitly work with threads when you want to support multiple clients. But for that you should use asynchronous calls (as opposed to synchronous, which are used in the tutorials you listed). Have a look at the asynchronous echo tcp server example, it serves multiple clients without using threads.

is boost creating a thread for each client somewhere inside?

When working with asynchronous calls, boost asio is doing these things behind the scenes. It could use threads, but it usually doesn't because there are other, preferred mechanisms for working with multiple sockets at once. For example on linux you have epoll, select and poll (in order of preference). I'm not sure what the situation is on windows, there might be other mechanisms or the preference order might be different. But in any case, boost asio takes care of this, chooses the best mechanism there is for your platform and hides it behind those asynchronous calls.