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- //
- // blocking_udp_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/io_context.hpp>
- #include <boost/asio/ip/udp.hpp>
- #include <cstdlib>
- #include <boost/bind.hpp>
- #include <iostream>
- using boost::asio::ip::udp;
- //----------------------------------------------------------------------
- //
- // 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::bind to specify the completion handler:
- //
- // +---------------+
- // | |
- // | receive |
- // | |
- // +---------------+
- // |
- // async_- | +----------------+
- // receive() | | |
- // +--->| handle_receive |
- // | |
- // +----------------+
- //
- // 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(const udp::endpoint& listen_endpoint)
- : socket_(io_context_, listen_endpoint)
- {
- }
- std::size_t receive(const boost::asio::mutable_buffer& buffer,
- boost::asio::chrono::steady_clock::duration timeout,
- boost::system::error_code& ec)
- {
- // Start the asynchronous operation. The handle_receive function used as a
- // callback will update the ec and length variables.
- std::size_t length = 0;
- socket_.async_receive(boost::asio::buffer(buffer),
- boost::bind(&client::handle_receive, _1, _2, &ec, &length));
- // Run the operation until it completes, or until the timeout.
- run(timeout);
- return length;
- }
- 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())
- {
- // Cancel the outstanding asynchronous operation.
- socket_.cancel();
- // Run the io_context again until the operation completes.
- io_context_.run();
- }
- }
- static void handle_receive(
- const boost::system::error_code& ec, std::size_t length,
- boost::system::error_code* out_ec, std::size_t* out_length)
- {
- *out_ec = ec;
- *out_length = length;
- }
- private:
- boost::asio::io_context io_context_;
- udp::socket socket_;
- };
- //----------------------------------------------------------------------
- int main(int argc, char* argv[])
- {
- try
- {
- using namespace std; // For atoi.
- if (argc != 3)
- {
- std::cerr << "Usage: blocking_udp_client <listen_addr> <listen_port>\n";
- return 1;
- }
- udp::endpoint listen_endpoint(
- boost::asio::ip::make_address(argv[1]),
- std::atoi(argv[2]));
- client c(listen_endpoint);
- for (;;)
- {
- char data[1024];
- boost::system::error_code ec;
- std::size_t n = c.receive(boost::asio::buffer(data),
- boost::asio::chrono::seconds(10), ec);
- if (ec)
- {
- std::cout << "Receive error: " << ec.message() << "\n";
- }
- else
- {
- std::cout << "Received: ";
- std::cout.write(data, n);
- std::cout << "\n";
- }
- }
- }
- catch (std::exception& e)
- {
- std::cerr << "Exception: " << e.what() << "\n";
- }
- return 0;
- }
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