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//
// blocking_tcp_client.cpp
// ~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2018 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/buffer.hpp>
#include <boost/asio/connect.hpp>
#include <boost/asio/io_context.hpp>
#include <boost/asio/ip/tcp.hpp>
#include <boost/asio/read_until.hpp>
#include <boost/system/system_error.hpp>
#include <boost/asio/write.hpp>
#include <cstdlib>
#include <iostream>
#include <string>
#include <boost/lambda/bind.hpp>
#include <boost/lambda/lambda.hpp>
using boost::asio::ip::tcp;
using boost::lambda::bind;
using boost::lambda::var;
using boost::lambda::_1;
using boost::lambda::_2;
//----------------------------------------------------------------------
//
// This class manages socket timeouts by running the io_context using the timed
// io_context::run_for() member function. Each asynchronous operation is given
// a timeout within which it must complete. The socket operations themselves
// use boost::lambda function objects as completion handlers. For a given
// socket operation, the client object runs the io_context to block thread
// execution until the operation completes or the timeout is reached. If the
// io_context::run_for() function times out, the socket is closed and the
// outstanding asynchronous operation is cancelled.
//
class client
{
public:
client()
: socket_(io_context_)
{
}
void connect(const std::string& host, const std::string& service,
boost::asio::chrono::steady_clock::duration timeout)
{
// Resolve the host name and service to a list of endpoints.
tcp::resolver::results_type endpoints =
tcp::resolver(io_context_).resolve(host, service);
// Start the asynchronous operation itself. The boost::lambda function
// object is used as a callback and will update the ec variable when the
// operation completes. The blocking_udp_client.cpp example shows how you
// can use boost::bind rather than boost::lambda.
boost::system::error_code ec;
boost::asio::async_connect(socket_, endpoints, var(ec) = _1);
// Run the operation until it completes, or until the timeout.
run(timeout);
// Determine whether a connection was successfully established.
if (ec)
throw boost::system::system_error(ec);
}
std::string read_line(boost::asio::chrono::steady_clock::duration timeout)
{
// Start the asynchronous operation. The boost::lambda function object is
// used as a callback and will update the ec variable when the operation
// completes. The blocking_udp_client.cpp example shows how you can use
// boost::bind rather than boost::lambda.
boost::system::error_code ec;
std::size_t n = 0;
boost::asio::async_read_until(socket_,
boost::asio::dynamic_buffer(input_buffer_),
'\n', (var(ec) = _1, var(n) = _2));
// Run the operation until it completes, or until the timeout.
run(timeout);
// Determine whether the read completed successfully.
if (ec)
throw boost::system::system_error(ec);
std::string line(input_buffer_.substr(0, n - 1));
input_buffer_.erase(0, n);
return line;
}
void write_line(const std::string& line,
boost::asio::chrono::steady_clock::duration timeout)
{
std::string data = line + "\n";
// Start the asynchronous operation. The boost::lambda function object is
// used as a callback and will update the ec variable when the operation
// completes. The blocking_udp_client.cpp example shows how you can use
// boost::bind rather than boost::lambda.
boost::system::error_code ec;
boost::asio::async_write(socket_, boost::asio::buffer(data), var(ec) = _1);
// Run the operation until it completes, or until the timeout.
run(timeout);
// Determine whether the read completed successfully.
if (ec)
throw boost::system::system_error(ec);
}
private:
void run(boost::asio::chrono::steady_clock::duration timeout)
{
// Restart the io_context, as it may have been left in the "stopped" state
// by a previous operation.
io_context_.restart();
// Block until the asynchronous operation has completed, or timed out. If
// the pending asynchronous operation is a composed operation, the deadline
// applies to the entire operation, rather than individual operations on
// the socket.
io_context_.run_for(timeout);
// If the asynchronous operation completed successfully then the io_context
// would have been stopped due to running out of work. If it was not
// stopped, then the io_context::run_for call must have timed out.
if (!io_context_.stopped())
{
// Close the socket to cancel the outstanding asynchronous operation.
socket_.close();
// Run the io_context again until the operation completes.
io_context_.run();
}
}
boost::asio::io_context io_context_;
tcp::socket socket_;
std::string input_buffer_;
};
//----------------------------------------------------------------------
int main(int argc, char* argv[])
{
try
{
if (argc != 4)
{
std::cerr << "Usage: blocking_tcp_client <host> <port> <message>\n";
return 1;
}
client c;
c.connect(argv[1], argv[2], boost::asio::chrono::seconds(10));
boost::asio::chrono::steady_clock::time_point time_sent =
boost::asio::chrono::steady_clock::now();
c.write_line(argv[3], boost::asio::chrono::seconds(10));
for (;;)
{
std::string line = c.read_line(boost::asio::chrono::seconds(10));
// Keep going until we get back the line that was sent.
if (line == argv[3])
break;
}
boost::asio::chrono::steady_clock::time_point time_received =
boost::asio::chrono::steady_clock::now();
std::cout << "Round trip time: ";
std::cout << boost::asio::chrono::duration_cast<
boost::asio::chrono::microseconds>(
time_received - time_sent).count();
std::cout << " microseconds\n";
}
catch (std::exception& e)
{
std::cerr << "Exception: " << e.what() << "\n";
}
return 0;
}
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