Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

doc/html/boost_asio/example/iostreams/http_client.cpp

//
// sync_client.cpp
// ~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2012 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 <iostream>
#include <istream>
#include <ostream>
#include <string>
#include <boost/asio/ip/tcp.hpp>

using boost::asio::ip::tcp;

int main(int argc, char* argv[])
{
  try
  {
    if (argc != 3)
    {
      std::cout << "Usage: http_client <server> <path>\n";
      std::cout << "Example:\n";
      std::cout << "  http_client www.boost.org /LICENSE_1_0.txt\n";
      return 1;
    }

    boost::asio::ip::tcp::iostream s;

    // The entire sequence of I/O operations must complete within 60 seconds.
    // If an expiry occurs, the socket is automatically closed and the stream
    // becomes bad.
    s.expires_from_now(boost::posix_time::seconds(60));

    // Establish a connection to the server.
    s.connect(argv[1], "http");
    if (!s)
    {
      std::cout << "Unable to connect: " << s.error().message() << "\n";
      return 1;
    }

    // Send the request. We specify the "Connection: close" header so that the
    // server will close the socket after transmitting the response. This will
    // allow us to treat all data up until the EOF as the content.
    s << "GET " << argv[2] << " HTTP/1.0\r\n";
    s << "Host: " << argv[1] << "\r\n";
    s << "Accept: */*\r\n";
    s << "Connection: close\r\n\r\n";

    // By default, the stream is tied with itself. This means that the stream
    // automatically flush the buffered output before attempting a read. It is
    // not necessary not explicitly flush the stream at this point.

    // Check that response is OK.
    std::string http_version;
    s >> http_version;
    unsigned int status_code;
    s >> status_code;
    std::string status_message;
    std::getline(s, status_message);
    if (!s || http_version.substr(0, 5) != "HTTP/")
    {
      std::cout << "Invalid response\n";
      return 1;
    }
    if (status_code != 200)
    {
      std::cout << "Response returned with status code " << status_code << "\n";
      return 1;
    }

    // Process the response headers, which are terminated by a blank line.
    std::string header;
    while (std::getline(s, header) && header != "\r")
      std::cout << header << "\n";
    std::cout << "\n";

    // Write the remaining data to output.
    std::cout << s.rdbuf();
  }
  catch (std::exception& e)
  {
    std::cout << "Exception: " << e.what() << "\n";
  }

  return 0;
}