beast/example/websocket/server/async/websocket_server_async.cpp
Damian Jarek 0f5d1edcd8 Fix data race in websocket examples
When using `websocket::stream`, the user has to take care to initiate
async operations within the associated strand.

Signed-off-by: Damian Jarek <damian.jarek93@gmail.com>
2019-10-06 07:52:13 -07:00

282 lines
7.1 KiB
C++

//
// Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail 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)
//
// Official repository: https://github.com/boostorg/beast
//
//------------------------------------------------------------------------------
//
// Example: WebSocket server, asynchronous
//
//------------------------------------------------------------------------------
#include <boost/beast/core.hpp>
#include <boost/beast/websocket.hpp>
#include <boost/asio/dispatch.hpp>
#include <boost/asio/strand.hpp>
#include <algorithm>
#include <cstdlib>
#include <functional>
#include <iostream>
#include <memory>
#include <string>
#include <thread>
#include <vector>
namespace beast = boost::beast; // from <boost/beast.hpp>
namespace http = beast::http; // from <boost/beast/http.hpp>
namespace websocket = beast::websocket; // from <boost/beast/websocket.hpp>
namespace net = boost::asio; // from <boost/asio.hpp>
using tcp = boost::asio::ip::tcp; // from <boost/asio/ip/tcp.hpp>
//------------------------------------------------------------------------------
// Report a failure
void
fail(beast::error_code ec, char const* what)
{
std::cerr << what << ": " << ec.message() << "\n";
}
// Echoes back all received WebSocket messages
class session : public std::enable_shared_from_this<session>
{
websocket::stream<beast::tcp_stream> ws_;
beast::flat_buffer buffer_;
public:
// Take ownership of the socket
explicit
session(tcp::socket&& socket)
: ws_(std::move(socket))
{
}
// Get on the correct executor
void
run()
{
// We need to be executing within a strand to perform async operations
// on the I/O objects in this session. Although not strictly necessary
// for single-threaded contexts, this example code is written to be
// thread-safe by default.
net::dispatch(ws_.get_executor(),
beast::bind_front_handler(
&session::on_run,
shared_from_this()));
}
// Start the asynchronous operation
void
on_run()
{
// Set suggested timeout settings for the websocket
ws_.set_option(
websocket::stream_base::timeout::suggested(
beast::role_type::server));
// Set a decorator to change the Server of the handshake
ws_.set_option(websocket::stream_base::decorator(
[](websocket::response_type& res)
{
res.set(http::field::server,
std::string(BOOST_BEAST_VERSION_STRING) +
" websocket-server-async");
}));
// Accept the websocket handshake
ws_.async_accept(
beast::bind_front_handler(
&session::on_accept,
shared_from_this()));
}
void
on_accept(beast::error_code ec)
{
if(ec)
return fail(ec, "accept");
// Read a message
do_read();
}
void
do_read()
{
// Read a message into our buffer
ws_.async_read(
buffer_,
beast::bind_front_handler(
&session::on_read,
shared_from_this()));
}
void
on_read(
beast::error_code ec,
std::size_t bytes_transferred)
{
boost::ignore_unused(bytes_transferred);
// This indicates that the session was closed
if(ec == websocket::error::closed)
return;
if(ec)
fail(ec, "read");
// Echo the message
ws_.text(ws_.got_text());
ws_.async_write(
buffer_.data(),
beast::bind_front_handler(
&session::on_write,
shared_from_this()));
}
void
on_write(
beast::error_code ec,
std::size_t bytes_transferred)
{
boost::ignore_unused(bytes_transferred);
if(ec)
return fail(ec, "write");
// Clear the buffer
buffer_.consume(buffer_.size());
// Do another read
do_read();
}
};
//------------------------------------------------------------------------------
// Accepts incoming connections and launches the sessions
class listener : public std::enable_shared_from_this<listener>
{
net::io_context& ioc_;
tcp::acceptor acceptor_;
public:
listener(
net::io_context& ioc,
tcp::endpoint endpoint)
: ioc_(ioc)
, acceptor_(ioc)
{
beast::error_code ec;
// Open the acceptor
acceptor_.open(endpoint.protocol(), ec);
if(ec)
{
fail(ec, "open");
return;
}
// Allow address reuse
acceptor_.set_option(net::socket_base::reuse_address(true), ec);
if(ec)
{
fail(ec, "set_option");
return;
}
// Bind to the server address
acceptor_.bind(endpoint, ec);
if(ec)
{
fail(ec, "bind");
return;
}
// Start listening for connections
acceptor_.listen(
net::socket_base::max_listen_connections, ec);
if(ec)
{
fail(ec, "listen");
return;
}
}
// Start accepting incoming connections
void
run()
{
do_accept();
}
private:
void
do_accept()
{
// The new connection gets its own strand
acceptor_.async_accept(
net::make_strand(ioc_),
beast::bind_front_handler(
&listener::on_accept,
shared_from_this()));
}
void
on_accept(beast::error_code ec, tcp::socket socket)
{
if(ec)
{
fail(ec, "accept");
}
else
{
// Create the session and run it
std::make_shared<session>(std::move(socket))->run();
}
// Accept another connection
do_accept();
}
};
//------------------------------------------------------------------------------
int main(int argc, char* argv[])
{
// Check command line arguments.
if (argc != 4)
{
std::cerr <<
"Usage: websocket-server-async <address> <port> <threads>\n" <<
"Example:\n" <<
" websocket-server-async 0.0.0.0 8080 1\n";
return EXIT_FAILURE;
}
auto const address = net::ip::make_address(argv[1]);
auto const port = static_cast<unsigned short>(std::atoi(argv[2]));
auto const threads = std::max<int>(1, std::atoi(argv[3]));
// The io_context is required for all I/O
net::io_context ioc{threads};
// Create and launch a listening port
std::make_shared<listener>(ioc, tcp::endpoint{address, port})->run();
// Run the I/O service on the requested number of threads
std::vector<std::thread> v;
v.reserve(threads - 1);
for(auto i = threads - 1; i > 0; --i)
v.emplace_back(
[&ioc]
{
ioc.run();
});
ioc.run();
return EXIT_SUCCESS;
}