echo_server.cpp

#include <boost/asio.hpp>
#include <boost/asio/awaitable.hpp>
#include <boost/asio/co_spawn.hpp>
#include <boost/asio/detached.hpp>
#include <boost/asio/use_awaitable.hpp>
#include <iostream>
#include <memory>

using boost::asio::awaitable;
using boost::asio::co_spawn;
using boost::asio::detached;
using boost::asio::use_awaitable;
using boost::asio::ip::tcp;

/**
 * @brief 协程式会话处理
 * 使用 co_await 进行异步读写，替代旧版回调式实现。
 */
awaitable<void> handleSession(tcp::socket socket)
{
	try
	{
		char data[1024];
		for (;;)
		{
			// 协程式异步读取
			auto bytesRead = co_await socket.async_read_some(boost::asio::buffer(data), use_awaitable);

			// 协程式异步写入（Echo 回写）
			co_await boost::asio::async_write(socket, boost::asio::buffer(data, bytesRead), use_awaitable);
		}
	}
	catch (const std::exception&)
	{
		// 连接关闭或错误，会话结束
	}
}

/**
 * @brief 协程式连接接受器
 */
awaitable<void> listener(tcp::acceptor acceptor)
{
	for (;;)
	{
		// 协程式异步接受连接
		auto socket = co_await acceptor.async_accept(use_awaitable);

		// 为每个连接启动一个独立的协程
		co_spawn(acceptor.get_executor(), handleSession(std::move(socket)), detached);
	}
}

int main(int argc, char* argv[])
{
	try
	{
		if (argc != 2)
		{
			std::cerr << "用法: echo_server <端口>\n";
			return 1;
		}

		boost::asio::io_context ioContext;

		auto port = static_cast<unsigned short>(std::atoi(argv[1]));
		tcp::acceptor acceptor(ioContext, tcp::endpoint(tcp::v4(), port));

		// 启动监听协程
		co_spawn(ioContext, listener(std::move(acceptor)), detached);

		std::cout << "Echo Server（协程式）启动在端口 " << argv[1] << std::endl;
		ioContext.run();
	}
	catch (const std::exception& e)
	{
		std::cerr << "异常: " << e.what() << std::endl;
	}

	return 0;
}