asio学习笔记-简单的http客户端

// asion_simple.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#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;
}
// 定义一个 io_service
boost::asio::io_service io_service;
// Get a list of endpoints corresponding to the server name.
// 定义一个域名解析器
tcp::resolver resolver(io_service);
//定义一个查询query
//	tcp::resolver::query query("www.baidu.com", "http");
tcp::resolver::query query("127.0.0.1", "8000");
//解析query,获得节点 但是不明白为什么需要迭代器
//节点应该只有0个或者1个
tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);
tcp::resolver::iterator end;
// Try each endpoint until we successfully establish a connection.
//定义socket并且连接
tcp::socket socket(io_service);
boost::system::error_code error = boost::asio::error::host_not_found;
while (error && endpoint_iterator != end)
{
socket.close();
socket.connect(*endpoint_iterator++, error);
}
if (error)
throw boost::system::system_error(error);
// 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.
//定义一个字符流，编辑HTTP 查询命令

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.
//发送查询命令
boost::asio::write(socket, request);
// Read the response status line.
//读取查询结果
boost::asio::streambuf response;
//读取http的文件头，然后返回
boost::asio::read_until(socket, response, "/r/n");
// Check that response is OK.
//获得http状态码
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.
//读取http头
boost::asio::read_until(socket, response, "/r/n/r/n");
// Process the response headers.
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.
//读取显示其他内容
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";
}
system("pause");
return 0;
}