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//
// process_per_connection.cpp
// ~~~~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2013 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_service.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_service& io_service, unsigned short port)
: io_service_(io_service),
signal_(io_service, SIGCHLD),
acceptor_(io_service, tcp::endpoint(tcp::v4(), port)),
socket_(io_service)
{
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_service that we are about to fork. The io_service cleans
// up any internal resources, such as threads, that may interfere with
// forking.
io_service_.notify_fork(boost::asio::io_service::fork_prepare);
if (fork() == 0)
{
// Inform the io_service that the fork is finished and that this is the
// child process. The io_service uses this opportunity to create any
// internal file descriptors that must be private to the new process.
io_service_.notify_fork(boost::asio::io_service::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_service that the fork is finished (or failed) and that
// this is the parent process. The io_service uses this opportunity to
// recreate any internal resources that were cleaned up during
// preparation for the fork.
io_service_.notify_fork(boost::asio::io_service::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_service& io_service_;
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_service io_service;
using namespace std; // For atoi.
server s(io_service, atoi(argv[1]));
io_service.run();
}
catch (std::exception& e)
{
std::cerr << "Exception: " << e.what() << std::endl;
}
}
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