| // |
| // blocking_tcp_client.cpp |
| // ~~~~~~~~~~~~~~~~~~~~~~~ |
| // |
| // Copyright (c) 2003-2021 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 "asio/buffer.hpp" |
| #include "asio/connect.hpp" |
| #include "asio/io_context.hpp" |
| #include "asio/ip/tcp.hpp" |
| #include "asio/read_until.hpp" |
| #include "asio/system_error.hpp" |
| #include "asio/write.hpp" |
| #include <cstdlib> |
| #include <iostream> |
| #include <string> |
| |
| using 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. |
| std::error_code error; |
| asio::async_connect(socket_, endpoints, |
| [&](const std::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. |
| std::error_code error; |
| std::size_t n = 0; |
| asio::async_read_until(socket_, |
| asio::dynamic_buffer(input_buffer_), '\n', |
| [&](const std::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. |
| std::error_code error; |
| asio::async_write(socket_, asio::buffer(data), |
| [&](const std::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(); |
| } |
| } |
| |
| 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; |
| } |