ASIO例子HTTP用戶端，同步的例子sync_client.cpp

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//// sync_client.cpp// ~~~~~~~~~~~~~~~//HTTP用戶端，同步// Copyright (c) 2003-2013 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.hpp>using boost::asio::ip::tcp;int main(int argc, char* argv[]){  try  {    if (argc != 3)    {      std::cout << "Usage: sync_client <server> <path>\n";      std::cout << "Example:\n";      std::cout << "  sync_client www.boost.org /LICENSE_1_0.txt\n";      return 1;    }    boost::asio::io_service io_service;    // Get a list of endpoints corresponding to the server name.    //解析網域名稱，擷取一個伺服器列表。使用迭代器訪問    tcp::resolver resolver(io_service);    //http的意思使用80連接埠    tcp::resolver::query query(argv[1], "http");    tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);    // Try each endpoint until we successfully establish a connection.    tcp::socket socket(io_service);    //串連，這裡貌似並沒有遍曆，只是假設第一個端點ok    boost::asio::connect(socket, endpoint_iterator);    // Form 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.    //構建HTTP頭部？指定Connectioin:close以達到傳輸完響應後立刻關閉socket。這樣可以允許    //我們把所有到EOF前資料當著內容    //關於streambuf,參考：http://www.boost.org/doc/libs/1_56_0/doc/html/boost_asio/reference/streambuf.html    //streambuf由std::streambuf派生而來，與streambuf的由一個或多個字元數組組成的輸入輸出序列相關。    //貌似可以對socket直接讀寫？    boost::asio::streambuf request;    std::ostream request_stream(&request);    request_stream << "GET " << argv[2] << " HTTP/1.0\r\n";    request_stream << "Host: " << argv[1] << "\r\n";    request_stream << "Accept: */*\r\n";    request_stream << "Connection: close\r\n\r\n";    // Send the request.    boost::asio::write(socket, request);    // Read the response status line. The response streambuf will automatically    // grow to accommodate the entire line. The growth may be limited by passing    // a maximum size to the streambuf constructor.    //讀取回應狀態行。響應streambuf將會自動成長直到完成整行。而且增長的長度限制在streambuf的max_size.    //即可能一次read_until受streambuf的大小限制無法讀完。    boost::asio::streambuf response;    boost::asio::read_until(socket, response, "\r\n");    // Check that response is OK.    //檢查響應報文，從響應報文讀取資料。    std::istream response_stream(&response);    std::string http_version;    response_stream >> http_version;    unsigned int status_code;    response_stream >> status_code;    std::string status_message;    std::getline(response_stream, status_message);    if (!response_stream || 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;    }    // Read the response headers, which are terminated by a blank line.    //讀回應標頭部，以空白行結束。    boost::asio::read_until(socket, response, "\r\n\r\n");    // Process the response headers.    //輸出回應標頭部    std::string header;    while (std::getline(response_stream, header) && header != "\r")      std::cout << header << "\n";    std::cout << "\n";    // Write whatever content we already have to output.    if (response.size() > 0)      std::cout << &response;    // Read until EOF, writing data to output as we go.    //不停地讀socket直到讀取完畢。    //transfer_at_least為一個函數對象。即讀到指定的位元組數便可以繼續下一次讀寫了。    boost::system::error_code error;    while (boost::asio::read(socket, response,          boost::asio::transfer_at_least(1), error))      std::cout << &response;    if (error != boost::asio::error::eof)      throw boost::system::system_error(error);  }  catch (std::exception& e)  {    std::cout << "Exception: " << e.what() << "\n";  }  return 0;}

 

ASIO例子HTTP用戶端，同步的例子sync_client.cpp