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- //
- // process_per_connection.cpp
- // ~~~~~~~~~~~~~~~~~~~~~~~~~~
- //
- // Copyright (c) 2003-2019 Christopher M. Kohlhoff (chris at kohlhoff dot com)
- //
- // Distributed under the Boost Software License, Version 1.0. (See accompanying
- // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
- //
- #include <boost/asio/io_context.hpp>
- #include <boost/asio/ip/tcp.hpp>
- #include <boost/asio/signal_set.hpp>
- #include <boost/asio/write.hpp>
- #include <boost/array.hpp>
- #include <boost/bind.hpp>
- #include <cstdlib>
- #include <iostream>
- #include <sys/types.h>
- #include <sys/wait.h>
- #include <unistd.h>
- using boost::asio::ip::tcp;
- class server
- {
- public:
- server(boost::asio::io_context& io_context, unsigned short port)
- : io_context_(io_context),
- signal_(io_context, SIGCHLD),
- acceptor_(io_context, tcp::endpoint(tcp::v4(), port)),
- socket_(io_context)
- {
- start_signal_wait();
- start_accept();
- }
- private:
- void start_signal_wait()
- {
- signal_.async_wait(boost::bind(&server::handle_signal_wait, this));
- }
- void handle_signal_wait()
- {
- // Only the parent process should check for this signal. We can determine
- // whether we are in the parent by checking if the acceptor is still open.
- if (acceptor_.is_open())
- {
- // Reap completed child processes so that we don't end up with zombies.
- int status = 0;
- while (waitpid(-1, &status, WNOHANG) > 0) {}
- start_signal_wait();
- }
- }
- void start_accept()
- {
- acceptor_.async_accept(socket_,
- boost::bind(&server::handle_accept, this, _1));
- }
- void handle_accept(const boost::system::error_code& ec)
- {
- if (!ec)
- {
- // Inform the io_context that we are about to fork. The io_context cleans
- // up any internal resources, such as threads, that may interfere with
- // forking.
- io_context_.notify_fork(boost::asio::io_context::fork_prepare);
- if (fork() == 0)
- {
- // Inform the io_context that the fork is finished and that this is the
- // child process. The io_context uses this opportunity to create any
- // internal file descriptors that must be private to the new process.
- io_context_.notify_fork(boost::asio::io_context::fork_child);
- // The child won't be accepting new connections, so we can close the
- // acceptor. It remains open in the parent.
- acceptor_.close();
- // The child process is not interested in processing the SIGCHLD signal.
- signal_.cancel();
- start_read();
- }
- else
- {
- // Inform the io_context that the fork is finished (or failed) and that
- // this is the parent process. The io_context uses this opportunity to
- // recreate any internal resources that were cleaned up during
- // preparation for the fork.
- io_context_.notify_fork(boost::asio::io_context::fork_parent);
- socket_.close();
- start_accept();
- }
- }
- else
- {
- std::cerr << "Accept error: " << ec.message() << std::endl;
- start_accept();
- }
- }
- void start_read()
- {
- socket_.async_read_some(boost::asio::buffer(data_),
- boost::bind(&server::handle_read, this, _1, _2));
- }
- void handle_read(const boost::system::error_code& ec, std::size_t length)
- {
- if (!ec)
- start_write(length);
- }
- void start_write(std::size_t length)
- {
- boost::asio::async_write(socket_, boost::asio::buffer(data_, length),
- boost::bind(&server::handle_write, this, _1));
- }
- void handle_write(const boost::system::error_code& ec)
- {
- if (!ec)
- start_read();
- }
- boost::asio::io_context& io_context_;
- boost::asio::signal_set signal_;
- tcp::acceptor acceptor_;
- tcp::socket socket_;
- boost::array<char, 1024> data_;
- };
- int main(int argc, char* argv[])
- {
- try
- {
- if (argc != 2)
- {
- std::cerr << "Usage: process_per_connection <port>\n";
- return 1;
- }
- boost::asio::io_context io_context;
- using namespace std; // For atoi.
- server s(io_context, atoi(argv[1]));
- io_context.run();
- }
- catch (std::exception& e)
- {
- std::cerr << "Exception: " << e.what() << std::endl;
- }
- }
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