How can I use Boost.Asio for asynchronous programming in C++?

How can I use Boost.Asio for asynchronous programming in C++?

Boost.Asio is a cross-platform C++ library for network and low-level I/O programming. It provides asynchronous I/O capabilities, which allow you to write non-blocking code. Would you like to see a simple example?

Yes, please provide a basic example of an asynchronous TCP server.

Here's a simple example of an asynchronous TCP server using Boost.Asio:

#include <boost/asio.hpp>
#include <iostream>

using boost::asio::ip::tcp;

void session(tcp::socket sock) {
    try {
        char data[1024];
        boost::system::error_code error;
        while (true) {
            size_t length = sock.read_some(boost::asio::buffer(data), error);
            if (error == boost::asio::error::eof) break; // Connection closed cleanly by peer.
            else if (error) throw boost::system::system_error(error); // Some other error.
            boost::asio::write(sock, boost::asio::buffer(data, length));
        }
    } catch (std::exception& e) {
        std::cerr << "Exception in thread: " << e.what() << std::endl;
    }
}

int main() {
    try {
        boost::asio::io_context io_context;
        tcp::acceptor acceptor(io_context, tcp::endpoint(tcp::v4(), 12345));
        while (true) {
            tcp::socket socket(io_context);
            acceptor.accept(socket);
            std::thread(session, std::move(socket)).detach();
        }
    } catch (std::exception& e) {
        std::cerr << "Exception: " << e.what() << std::endl;
    }
}

This code sets up a TCP server that echoes back any data it receives.

What if I want to implement an asynchronous client instead?

For an asynchronous TCP client, you can use the following example:

#include <boost/asio.hpp>
#include <iostream>

using boost::asio::ip::tcp;

void connect(tcp::resolver::results_type endpoints) {
    boost::asio::io_context io_context;
    tcp::socket socket(io_context);
    boost::asio::connect(socket, endpoints);
    std::string message = "Hello from client!";
    boost::asio::write(socket, boost::asio::buffer(message));
    char reply[1024];
    size_t reply_length = boost::asio::read(socket, boost::asio::buffer(reply, message.size()));
    std::cout << "Reply: " << std::string(reply, reply_length) << std::endl;
}

int main() {
    try {
        boost::asio::io_context io_context;
        tcp::resolver resolver(io_context);
        auto endpoints = resolver.resolve("127.0.0.1", "12345");
        connect(endpoints);
    } catch (std::exception& e) {
        std::cerr << "Exception: " << e.what() << std::endl;
    }
}

This client connects to the server, sends a message, and waits for a reply.