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- //
- // blocking_tcp_client.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/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>
- using boost::asio::ip::tcp;
- //----------------------------------------------------------------------
- //
- // 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 lambdas 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:
- void connect(const std::string& host, const std::string& service,
- std::chrono::steady_clock::duration timeout)
- {
- // Resolve the host name and service to a list of endpoints.
- auto endpoints = tcp::resolver(io_context_).resolve(host, service);
- // Start the asynchronous operation itself. The lambda that is used as a
- // callback will update the error variable when the operation completes.
- // The blocking_udp_client.cpp example shows how you can use std::bind
- // rather than a lambda.
- boost::system::error_code error;
- boost::asio::async_connect(socket_, endpoints,
- [&](const boost::system::error_code& result_error,
- const tcp::endpoint& /*result_endpoint*/)
- {
- error = result_error;
- });
- // Run the operation until it completes, or until the timeout.
- run(timeout);
- // Determine whether a connection was successfully established.
- if (error)
- throw std::system_error(error);
- }
- std::string read_line(std::chrono::steady_clock::duration timeout)
- {
- // Start the asynchronous operation. The lambda that is used as a callback
- // will update the error and n variables when the operation completes. The
- // blocking_udp_client.cpp example shows how you can use std::bind rather
- // than a lambda.
- boost::system::error_code error;
- std::size_t n = 0;
- boost::asio::async_read_until(socket_,
- boost::asio::dynamic_buffer(input_buffer_), '\n',
- [&](const boost::system::error_code& result_error,
- std::size_t result_n)
- {
- error = result_error;
- n = result_n;
- });
- // Run the operation until it completes, or until the timeout.
- run(timeout);
- // Determine whether the read completed successfully.
- if (error)
- throw std::system_error(error);
- std::string line(input_buffer_.substr(0, n - 1));
- input_buffer_.erase(0, n);
- return line;
- }
- void write_line(const std::string& line,
- std::chrono::steady_clock::duration timeout)
- {
- std::string data = line + "\n";
- // Start the asynchronous operation itself. The lambda that is used as a
- // callback will update the error variable when the operation completes.
- // The blocking_udp_client.cpp example shows how you can use std::bind
- // rather than a lambda.
- boost::system::error_code error;
- boost::asio::async_write(socket_, boost::asio::buffer(data),
- [&](const boost::system::error_code& result_error,
- std::size_t /*result_n*/)
- {
- error = result_error;
- });
- // Run the operation until it completes, or until the timeout.
- run(timeout);
- // Determine whether the read completed successfully.
- if (error)
- throw std::system_error(error);
- }
- private:
- void run(std::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_{io_context_};
- 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], std::chrono::seconds(10));
- auto time_sent = std::chrono::steady_clock::now();
- c.write_line(argv[3], std::chrono::seconds(10));
- for (;;)
- {
- std::string line = c.read_line(std::chrono::seconds(10));
- // Keep going until we get back the line that was sent.
- if (line == argv[3])
- break;
- }
- auto time_received = std::chrono::steady_clock::now();
- std::cout << "Round trip time: ";
- std::cout << std::chrono::duration_cast<
- std::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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